Odorant Binding Proteins
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Odorant Binding Proteins
This is about invertebrate odorant binding proteins, in particular in insects.
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A possible role of DNA methylation in functional divergence of a fast evolving duplicate gene encoding odorant binding protein 11 in the honeybee

A possible role of DNA methylation in functional divergence of a fast evolving duplicate gene encoding odorant binding protein 11 in the honeybee | Odorant Binding Proteins | Scoop.it
Although gene duplication is seen as the main path to evolution of new functions, molecular mechanisms by which selection favours the gain versus loss of newly duplicated genes and minimizes the fixation of pseudo-genes are not well understood. Here, we investigate in detail a duplicate honeybee gene obp11 belonging to a fast evolving insect gene family encoding odorant binding proteins (OBPs). We report that obp11 is expressed only in female bees in rare antennal sensilla basiconica in contrast to its tandem partner obp10 that is expressed in the brain in both females and males (drones). Unlike all other obp genes in the honeybee, obp11 is methylated suggesting that functional diversification of obp11 and obp10 may have been driven by an epigenetic mechanism. We also show that increased methylation in drones near one donor splice site that correlates with higher abundance of a transcript variant encoding a truncated OBP11 protein is one way of controlling its contrasting expression. Our data suggest that like in mammals and plants, DNA methylation in insects may contribute to functional diversification of proteins produced from duplicated genes, in particular to their subfunctionalization by generating complementary patterns of expression.
Bernard Offmann's insight:
Very nice paper. Fast duplicate gene diversification may have been driven, in part, by an epigenetic mechanism.
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Genome-wide identification and characterization of odorant-binding protein (OBP) genes in the malaria vector Anopheles sinensis (Diptera: Culicidae)

Insect Sci. 2016 Mar 11. doi: 10.1111/1744-7917.12333. [Epub ahead of print]

Xiu He, Zheng Bo He, Yu Juan Zhang, Yong Zhou, Peng Jie Xian, Liang Qiao and Bin Chen

Abstract 

Anopheles sinensis is a major malaria vector. Insect Odorant-Binding Proteins (OBPs) may function in the reception of odorants in the olfactory system. The classification and characterization of the An. sinensis OBP genes have not been systematically studied. In this study, 64 putative OBP genes were identified in whole-genome level of An. sinensis based on the comparison between OBP conserved motifs, PBP_GOBP, and phylogenetic analysis with An. gambiae OBPs. The characterization of An. sinensis OBPs, including the motif's conservation, gene structure, genomic organization and classification, were investigated. A new gene, AsOBP73, belonging to the Plus-C subfamily, was identified with the support of transcript and conservative motifs. These An. sinensis OBP genes were classified into 3 subfamilies with 37, 15 and 12 genes in the subfamily Classic, Atypical and Plus-C, respectively. The genomic organization of An. sinensis OBPs suggests a clustered distribution across 9 different scaffolds. Eight genes (OBP23-28, OBP63-64) might originate from a single gene through a series of historic duplication events at least before divergence of Anopheles, Culex and Aedes. The microsynteny analyses indicate a very high synteny between An. sinensis and An. gambiae OBPs. OBP70 and OBP71 earlier classified under Plus-C in An. gambiae are recognized as belonging to the group Obp59a of the Classic subfamily, and OBP69 earlier classified under Plus-C has been moved to the Atypical subfamily in this study. The study established a basic information frame for further study of the OBP genes in insects as well as in An. sinensis.
Bernard Offmann's insight:
From Chen's team in  Chongqing (China), a very nice survey of another Anopheles species (An. sinensis) genome for odorant binding proteins. It contains 64 OBPs among which 37 are from the classic subfamily, 12 are from the PlusC subfamily and 15 from the "two-domains" or "atypical" subfamily. Distribution of OBPs shows co-linearity with that in An. gambiae.
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Analysis of antennal transcriptome and odorant binding protein expression profiles of the recently identified parasitoid wasp, Sclerodermus sp.

Comp Biochem Physiol Part D Genomics Proteomics. 2015 Jul 2;16:10-19. doi: 10.1016/j.cbd.2015.06.003. [Epub ahead of print]

 

Zhou CX, Min SF, Yan-Long T, Wang MQ.

 

Abstract

 

We constructed an antennal transcriptome of the parasitoid wasp, Sclerodermus sp. (Hymenoptera: Bethylidae). Our analysis of the transcriptome yielded 51,830,552 clean reads. A total of 46,269 unigenes were assembled, among which 29,582 unigenes exhibited significant similarity (E-values≤10-5) to sequences in the NCBI nonredundant protein database. Gene ontology (GO) and cluster of orthologous groups (COG) analyses were used for the functional classification of these unigenes. We identified ten odorant binding proteins (OBPs), ten chemosensory proteins (CSPs), eight olfactory receptors (ORs), three ionotropic receptors (IRs), six gustatory receptors (GRs), and two sensory neuron membrane proteins (SNMPs). The expression profiles of the ten OBPs were determined based on a qPCR analysis of RNA extracted from the antennae, legs, and abdomens of wingless and winged female adults and whole larvae and pupae. The highest levels of OBP5, OBP6, OBP7, and OBP9 expression were observed in the antennae of adult females. The highest levels of OBP1, OBP2, and OBP4 expression were observed in the abdomen of winged females. The highest levels of OBP3 and OBP10 expression were observed in larvae and pupae, respectively, whereas OBP8 was expressed at high levels in both larvae and pupae. Our findings establish a foundation for future studies of the molecular mechanisms of chemosensory perception in Sclerodermus sp.

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The Lepidoptera Odorant Binding Protein gene family: Gene gain and loss within the GOBP/PBP complex of moths and butterflies

Insect Biochem Mol Biol. 2015 Jul;62:142-53. doi: 10.1016/j.ibmb.2015.03.003. Epub 2015 Mar 14.

 

Vogt RG1, Große-Wilde E2, Zhou JJ3.

 

Abstract

 

Butterflies and moths differ significantly in their daily activities: butterflies are diurnal while moths are largely nocturnal or crepuscular. This life history difference is presumably reflected in their sensory biology, and especially the balance between the use of chemical versus visual signals. Odorant Binding Proteins (OBP) are a class of insect proteins, at least some of which are thought to orchestrate the transfer of odor molecules within an olfactory sensillum (olfactory organ), between the air and odor receptor proteins (ORs) on the olfactory neurons. A Lepidoptera specific subclass of OBPs are the GOBPs and PBPs; these were the first OBPs studied and have well documented associations with olfactory sensilla. We have used the available genomes of two moths, Manduca sexta and Bombyx mori, and two butterflies, Danaus plexippus and Heliconius melpomene, to characterize the GOBP/PBP genes, attempting to identify gene orthologs and document specific gene gain and loss. First, we identified the full repertoire of OBPs in the M. sexta genome, and compared these with the full repertoire of OBPs from the other three lepidopteran genomes, the OBPs of Drosophila melanogaster and select OBPs from other Lepidoptera. We also evaluated the tissue specific expression of the M. sexta OBPs using an available RNAseq databases. In the four lepidopteran species, GOBP2 and all PBPs reside in single gene clusters; in two species GOBP1 is documented to be nearby, about 100 kb from the cluster; all GOBP/PBP genes share a common gene structure indicating a common origin. As such, the GOBP/PBP genes form a gene complex. Our findings suggest that (1) the lepidopteran GOBP/PBP complex is a monophyletic lineage with origins deep within Lepidoptera phylogeny, (2) within this lineage PBP gene evolution is much more dynamic than GOBP gene evolution, and (3) butterflies may have lost a PBP gene that plays an important role in moth pheromone detection, correlating with a shift from olfactory (moth) to visual (butterfly) communication, at least regarding long distance mate recognition. These findings will be clarified by additional lepidopteran genomic data, but the observation that moths and butterflies share most of the PBP/GOBP genes suggests that they also share common chemosensory-based behavioral pathways.

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The Anopheles stephensi odorant binding protein 1 (AsteObp1) gene: a new molecular marker for biological forms diagnosis

Acta Trop. 2015 Jun;146:101-13. doi: 10.1016/j.actatropica.2015.03.012. Epub 2015 Mar 17.

 

Gholizadeh S1, Firooziyan S2, Ladonni H3, Hajipirloo HM4, Djadid ND5, Hosseini A6, Raz A7.

 

Abstract

 

Anopheles (Cellia) stephensi Liston 1901 is known as an Asian malaria vector. Three biological forms, namely "mysorensis", "intermediate", and "type" have been earlier reported in this species. Nevertheless, the present morphological and molecular information is insufficient to diagnose these forms. During this investigation, An. stephensi biological forms were morphologically identified and sequenced for odorant-binding protein 1 (Obp1) gene. Also, intron I sequences were used to construct phylogenetic trees. Despite nucleotide sequence variation in exon of AsteObp1, nearly 100% identity was observed at the amino acid level among the three biological forms. In order to overcome difficulties in using egg morphology characters, intron I sequences of An. stephensi Obp1 opens new molecular way to the identification of the main Asian malaria vector biological forms. However, multidisciplinary studies are needed to establish the taxonomic status of An. stephensi.

Bernard Offmann's insight:

Odorant Binding Protein as molecular marker to discriminate mosquito types of Anopheles stephensi species, never thought of it. Cool !

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Olfactory biosensor for insect semiochemicals analysis by impedance sensing of odorant-binding proteins on interdigitated electrodes

Biosens Bioelectron. 2015 May 15;67:662-9. doi: 10.1016/j.bios.2014.09.098. Epub 2014 Oct 7.

 

Olfactory biosensor for insect semiochemicals analysis by impedance sensing of odorant-binding proteins on interdigitated electrodes.

 

Lu Y, Yao Y, Zhang Q, Zhang D, Zhuang S, Li H, Liu Q.

 

Abstract

 

Insects can sensitively and selectively detect thousands of semiochemicals at very low concentrations by their remarkable olfactory systems. As one of the most important olfactory proteins, odorant-binding proteins (OBPs) from insects are the most promising candidates for fabricating biosensors to detect biochemical molecules in the chemical ecology as well as for other biotechnological applications. In this study, we designed an olfactory biosensor by immobilizing OBPs from oriental fruit fly on interdigitated electrodes to detect semiochemicals. After successfully separated and purified, OBPs were immobilized by the special designed polyethylene glycol (PEG), SH-PEG-COOH, to produce a robust sensing membrane. Based on electrochemical sensing, interactions between OBPs and different semiochemicals emitted from host plants of the insect, such as the isoamyl acetate, β-ionone, and benzaldehyde, could be sensitively detected. With related amino acid residues in the hydrophobic cavities distinguished, the interaction forces between semiochemicals and OBPs were analyzed by molecular docking. Integrated biological olfaction proteins of insects, OBPs based biosensors could not only advance the progress in the understanding of chemical communication systems of insects, but also show promising potentials for biosensing applications in many fields.

Bernard Offmann's insight:

Another proof of concept of a biosensor on the road to a bio-based electronic nose.

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Two subclasses of odorant-binding proteins in Spodoptera exigua display structural conservation and functional divergence

Insect Mol Biol. 2015 Apr;24(2):167-82. doi: 10.1111/imb.12143. Epub 2014 Oct 24.

 

Liu NY1, Yang F, Yang K, He P, Niu XH, Xu W, Anderson A, Dong SL.

 

Abstract

 

Although many studies on lepidopteran pheromone-binding proteins (PBPs)/ general odorant-binding proteins (GOBPs) have been reported, the functional differentiation within and between the two odorant-binding protein (OBP) subclasses is still elusive. Here we conducted a comparative study on three SexiPBPs and two SexiGOBPs in Spodoptera exigua. Results showed that all five SexiPBP/GOBP genes have the same intron numbers and conserved exon/intron splice sites. Reverse transcription PCR results showed that these five SexiPBP/GOBPs were primarily expressed in antennae of both sexes and some were also detected in other tissues. Further, quantitative real-time PCR showed that five SexiPBP/GOBPs had different sex-biased expression patterns, with PBP1 being highly male-biased (5.96-fold difference) and PBP3 slightly female-biased (2.43-fold difference), while PBP2 and two GOBPs were approximately sex-equivalent (the absolute value<1.90-fold difference). Binding assays showed that all three SexiPBPs could bind all six sex pheromone components, but SexiPBP1 had much higher affinities [dissociation constant (Ki ) 1.20 μM). Very intriguingly, SexiGOBP2 displayed even stronger binding to five sex pheromone components (Ki <0.40 μM) than SexiPBP1. In contrast, SexiGOBP1 only exhibited weak binding to three alcohol-pheromone components. Similar results were obtained for tested pheromone analogues. In addition, each of SexiPBP/GOBPs selectively bound some plant odorants with considerable affinities (Ki <10.0 μM). Taken together, of the three SexiPBPs, SexiPBP1 may play the most important role in female sex pheromone reception, and additionally all three SexiPBPs can detect some plant odorants, while SexiGOBP2 may be involved in the detection of female sex pheromones in addition to plant odorants. The results strongly suggest functional differentiation within and between the two OBP sub-classes.

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Identification of candidate chemosensory genes in the antennal transcriptome of Tenebrio molitor (Coleoptera: Tenebrionidae)

Comp Biochem Physiol Part D Genomics Proteomics. 2015 Mar;13:44-51. doi: 10.1016/j.cbd.2015.01.004. Epub 2015 Feb 2.Liu S, Rao XJ, Li MY, Feng MF, He MZ, Li SG. Abstract

We present the first antennal transcriptome sequencing information for the yellow mealworm beetle, Tenebrio molitor (Coleoptera: Tenebrionidae). Analysis of the transcriptome dataset obtained 52,216,616 clean reads, from which 35,363 unigenes were assembled. Of these, 18,820 unigenes showed significant similarity (E-value <10(-5)) to known proteins in the NCBI non-redundant protein database. Gene ontology (GO) and Cluster of Orthologous Groups (COG) analyses were used for functional classification of these unigenes. We identified 19 putative odorant-binding protein (OBP) genes, 12 chemosensory protein (CSP) genes, 20 olfactory receptor (OR) genes, 6 ionotropic receptor (IR) genes and 2 sensory neuron membrane protein (SNMP) genes. BLASTX best hit results indicated that these chemosensory genes were most identical to their respective orthologs from Tribolium castaneum. Phylogenetic analyses also revealed that the T. molitor OBPs and CSPs are closely related to those of T. castaneum. Real-time quantitative PCR assays showed that eight TmolOBP genes were antennae-specific. Of these, TmolOBP5, TmolOBP7 and TmolOBP16 were found to be predominantly expressed in male antennae, while TmolOBP17 was expressed mainly in the legs of males. Several other genes were identified that were neither tissue-specific nor sex-specific. These results establish a firm foundation for future studies of the chemosensory genes in T. molitor.

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Easy to use plastic optical fiber-based biosensor for detection of butanal

PLoS One. 2015 Mar 19;10(3):e0116770. doi: 10.1371/journal.pone.0116770. eCollection 2015.Cennamo N, Di Giovanni S, Varriale A, Staiano M, Di Pietrantonio F, Notargiacomo A, Zeni L, D'Auria S. Abstract

The final goal of this work is to achieve a selective detection of butanal by the realization of a simple, small-size and low cost experimental approach. To this end, a porcine odorant-binding protein was used in connection with surface plasmon resonance transduction in a plastic optical fiber tool for the selective detection of butanal by a competitive assay. This allows to reduce the cost and the size of the sensing device and it offers the possibility to design a "Lab-on-a-chip" platform. The obtained results showed that this system approach is able to selectively detect the presence of butanal in the concentration range from 20 μM to 1000 μM.

Bernard Offmann's insight:

This is really a nice methodological & technical advancement. Towards electronic nose !

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Proteomic Analysis of Pig (Sus scrofa) Olfactory Soluble Proteome Reveals O-Linked-N-Acetylglucosaminylation of Secreted Odorant-Binding Proteins

Abstract

The diversity of olfactory binding proteins (OBPs) is a key point to understand their role in molecular olfaction. Since only few different sequences were characterized in each mammalian species, they have been considered as passive carriers of odors and pheromones. We have explored the soluble proteome of pig nasal mucus, taking benefit of the powerful tools of proteomics. Combining two-dimensional electrophoresis, mass spectrometry, and western-blot with specific antibodies, our analyses revealed for the first time that the pig nasal mucus is mainly composed of secreted OBP isoforms, some of them being potentially modified by O-GlcNAcylation. An ortholog gene of the glycosyltransferase responsible of the O-GlcNAc linking on extracellular proteins in Drosophila and Mouse (EOGT) was amplified from tissues of pigs of different ages and sex. The sequence was used in a phylogenetic analysis, which evidenced conservation of EOGT in insect and mammalian models studied in molecular olfaction. Extracellular O-GlcNAcylation of secreted OBPs could finely modulate their binding specificities to odors and pheromones. This constitutes a new mechanism for extracellular signaling by OBPs, suggesting that they act as the first step of odor discrimination.

Bernard Offmann's insight:

This is a very nice work. 

 

I would have never suspected that porcine odorant binding proteins would be O-GlcNAcylated though it was known from

another Patricia Nagnan-Le Meillour's work that they are phosphorylated.


Is there any chance that OBPs from invertebrates are also post-translationally modified ?

 

Authors point interest to search for OBP O-GlcNAcylation in insects, as a potential mechanism for odor discrimination by OBPs.

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Capacitance-modulated transistor detects odorant binding protein chiral interactions.

Capacitance-modulated transistor detects odorant binding protein chiral interactions. | Odorant Binding Proteins | Scoop.it

Mohammad Yusuf Mulla,Elena Tuccori,Maria Magliulo,Gianluca Lattanzi,Gerardo Palazzo, Krishna Persaud& Luisa Torsi

 

Nat. Commun. 6:6010 doi: 10.1038/ncomms7010 (2015).

 

Peripheral events in olfaction involve odorant binding proteins (OBPs) whose role in the recognition of different volatile chemicals is yet unclear. Here we report on the sensitive and quantitative measurement of the weak interactions associated with neutral enantiomers differentially binding to OBPs immobilized through a self-assembled monolayer to the gate of an organic bio-electronic transistor. The transduction is remarkably sensitive as the transistor output current is governed by the small capacitance of the protein layer undergoing minute changes as the ligand–protein complex is formed. Accurate determination of the free-energy balances and of the capacitance changes associated with the binding process allows derivation of the free-energy components as well as of the occurrence of conformational events associated with OBP ligand binding. Capacitance-modulated transistors open a new pathway for the study of ultra-weak molecular interactions in surface-bound protein–ligand complexes through an approach that combines bio-chemical and electronic thermodynamic parameters.

Bernard Offmann's insight:

Wow ! very nice work.

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Operating Mechanism and Molecular Dynamics of Pheromone-Binding Protein ASP1 as Influenced by pH

Operating Mechanism and Molecular Dynamics of Pheromone-Binding Protein ASP1 as Influenced by pH | Odorant Binding Proteins | Scoop.it

Odorant binding protein (OBP) is a vital component of the olfactory sensation system. It performs the specific role of ferrying odorant molecules to odorant receptors. OBP helps insects and types of animal to sense and transport stimuli molecules. However, the molecular details about how OBPs bind or release its odorant ligands are unclear. For some OBPs, the systems' pH level is reported to impact on the ligands' binding or unbinding capability. In this work we investigated the operating mechanism and molecular dynamics in bee antennal pheromone-binding protein ASP1 under varying pH conditions. We found that conformational flexibility is the key factor for regulating the interaction of ASP1 and its ligands, and the odorant binds to ASP1 at low pH conditions. Dynamics, once triggered by pH changes, play the key roles in coupling the global conformational changes with the odorant release. In ASP1, the C-terminus, the N-terminus, helix α2 and the region ranging from helices α4 to α5 form a cavity with a novel ‘entrance’ of binding. These are the major regions that respond to pH change and regulate the ligand release. Clearly there are processes of dynamics and hydrogen bond network propagation in ASP1 in response to pH stimuli. These findings lead to an understanding of the mechanism and dynamics of odorant-OBP interaction in OBP, and will benefit chemsensory-related biotech and agriculture research and development.

Bernard Offmann's insight:

This in part confirms our observations on mosquito OBP1 (http://www.tandfonline.com/doi/abs/10.1080/07391102.2013.834118)

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Crystal structure of the Locusta migratoria odorant binding protein

Locusta migratoria (Lmig) causes enormous losses to agricultural products, especially because it often infests the world with great swarms as locust plagues. Locusts find their plant hosts on which they feed through their olfactory system, in which odorant binding proteins (OBPs) play an important role. Previous study indicated that the amino acid sequences of LmigOBP showed low similarity to OBPs from other insect orders and we speculated that it might perform unique binding behavior. Here, we solved the first LmigOBP1 structure at 1.65 Å, which is a monomer in solution and disulfide bonds play a key role in maintaining its function. We show that LmigOBP1 possesses a unique seventh α-helix, which is located at the surface with strong interactions with the LmigOBP1 scaffold consisting of other six α-helices. Moreover, the seventh α-helix forms a wall of an “L” shaped internal hydrophobic cavity to accommodate linear ligands, which is consistent with the binding experiments. We also demonstrate that the ligand-binding pocket in LmigOBP1 is greatly different from that in the closest homologs mosquito OBPs. Taken together, this study provides a structural basis for designing small inhibitors to control locust.

Bernard Offmann's insight:

A new crystal structure for an insect OBP featuring a 7th helix that is involved in defining the binding cavity.

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Evaluation of the Activity of the Essential Oil from an Ornamental Flower against Aedes aegypti: Electrophysiology, Molecular Dynamics and Behavior...

PLoS One. 2016 Feb 29;11(2):e0150008. doi: 10.1371/journal.pone.0150008. eCollection 2016.

Patrícia C. Bezerra-Silva , Kamilla A. Dutra, Geanne K. N. Santos, Rayane C. S. Silva, Jorge Iulek, Paulo Milet-Pinheiro, Daniela M. A. F. Navarro

Abstract 

Dengue fever has spread worldwide and affects millions of people every year in tropical and subtropical regions of Africa, Asia, Europe and America. Since there is no effective vaccine against the dengue virus, prevention of disease transmission depends entirely on regulating the vector (Aedes aegypti) or interrupting human-vector contact. The aim of this study was to assess the oviposition deterrent activity of essential oils of three cultivars of torch ginger (Etlingera elatior, Zingiberaceae) against the dengue mosquito. Analysis of the oils by gas chromatography (GC)-mass spectrometry revealed the presence of 43 constituents, of which α-pinene, dodecanal and n-dodecanol were the major components in all cultivars. Solutions containing 100 ppm of the oils exhibited oviposition deterrent activities against gravid Ae. aegypti females. GC analysis with electroantennographic detection indicated that the oil constituents n-decanol, 2-undecanone, undecanal, dodecanal, trans-caryophyllene, (E)-β-farnesene, α-humulene, n-dodecanol, isodaucene and dodecanoic acid were able to trigger antennal depolarization in Ae. aegypti females. Bioassays confirmed that solutions containing 50 ppm of n-dodecanol or dodecanal exhibited oviposition deterrent activities, while a solution containing the alcohol and aldehyde in admixture at concentrations representative of the oil presented an activity similar to that of the 100 ppm oil solution. Docking and molecular dynamics simulations verified that the interaction energies of the long-chain oil components and Ae. aegypti odorant binding protein 1 were quite favorable, indicating that the protein is a possible oviposition deterrent receptor in the antenna of Ae. aegypti.
Bernard Offmann's insight:
Female tiger mosquito blocked from laying eggs after using ginger essential oil which causes antennal depolarization. Interestingly, OBP can bind quite long fatty acids such as 12 carbon dodecanol.
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Three amino acid residues of an odorant-binding protein are involved in binding odours in Loxostege sticticalis L.

Insect Mol Biol. 2015 Jul 8. doi: 10.1111/imb.12179. [Epub ahead of print]

 

Yin J, Zhuang X, Wang Q, Cao Y, Zhang S, Xiao C, Li K. 

 

Abstract

 

Odorant-binding proteins (OBPs) play an important role in insect olfactory processes and are thought to be responsible for the transport of pheromones and other semiochemicals across the sensillum lymph to the olfactory receptors within the antennal sensilla. As an important general odorant binding protein in the process of olfactory recognition, LstiGOBP1 of Loxostege sticticalis L. has been shown to have good affinity to various plant volatiles. However, the binding specificity of LstiGOBP1 should be further explored in order to better understand the olfactory recognition mechanism of L. sticticalis. In this study, real-time PCR experiments indicated that LstiGOBP1 was expressed primarily in adult antennae. Homology modelling and molecular docking were then conducted on the interactions between LstiGOBP1 and 1-heptanol to understand the interactions between LstiGOBP1 and their ligands. Hydrogen bonds formed by amino acid residues might be crucial for the ligand-binding specificity on molecular docking, a hypothesis that was tested by site-directed mutagenesis. As predicted binding sites for LstiGOBP1, Thr15, Trp43 and Val14 were replaced by alanine to determine the changes in binding affinity. Finally, fluorescence assays revealed that the mutants Thr15 and Trp43 had significantly decreased binding affinity to most odours; in mutants that had two-site mutations, the binding to the six odours that were tested was completely abolished. This result indicates that Thr15 and Trp43 were involved in binding these compounds, possibly by forming multiple hydrogen bonds with the functional groups of the ligands. These results provide new insights into the detailed chemistry of odours' interactions with proteins.

 

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Odorant-binding proteins display high affinities for behavioral attractants and repellents in the natural predator Chrysopa pallens.

Comp Biochem Physiol A Mol Integr Physiol. 2015 Jul;185:51-7. doi: 10.1016/j.cbpa.2015.03.011. Epub 2015 Mar 22.Li ZQ, Zhang S, Luo JY, Wang SB, Dong SL, Cui JJ. Abstract

 

Chrysopa pallens is an important natural predator of various pests in many different cropping systems. Understanding the sophisticated olfactory system of insect antennae is crucial for studying the physiological bases of olfaction and could also help enhance the effectiveness of C. pallens in biological control. However, functional studies of the olfactory genes in C. pallens are still lacking. In this study, we cloned five odorant-binding protein (OBP) genes from C. pallens (CpalOBPs). Quantitative RT-PCR results indicated that the five CpalOBPs had different tissue expression profiles. Ligand-binding assays showed that farnesol, farnesene, cis-3-hexenyl hexanoate, geranylacetone, beta-ionone, octyl aldehyde, decanal, nerolidol (Ki<20 μM), and especially 2-pentadecanone (Ki=1.19 μM) and 2-hexyl-1-decanol (Ki=0.37 μM) strongly bound to CpalOBP2. CpalOBP15 exhibited high binding affinities for beta-ionone, 2-tridecanone, trans-nerolidol, and dodecyl aldehyde. Behavioral trials using the 14 compounds exhibiting high binding affinities for the CpalOBPs revealed that nine were able to elicit significant behavioral responses from C. pallens. Among them, farnesene and its corresponding alcohol, farnesol, elicited remarkable repellent behavioral responses from C. pallens. Our study provides several compounds that could be selected to develop slow-release agents that attract/repel C. pallens and to improve the search for strategies to eliminate insect pests.

 

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Proteomic analysis of immunogenic proteins from salivary glands of Aedes aegypti

J Infect Public Health. 2015 Jun 6. pii: S1876-0341(15)00089-1. doi: 10.1016/j.jiph.2015.04.022. [Epub ahead of print]

 

Oktarianti R1, Senjarini K2, Hayano T3, Fatchiyah F4, Aulanni'am5.

 

Abstract

 

Humans develop anti-salivary proteins after arthropod bites or exposure to insect salivary proteins. This reaction indicates that vector bites have a positive effect on the host immune response, which can be used as epidemiological markers of exposure to the vector. Our previous study identified two immunogenic proteins with molecular weights of 31kDa and 56kDa from salivary gland extract (SGE) of Aedes aegypti that cross-reacted with serum samples from Dengue Hemorrhagic Fever (DHF) patients and healthy people in an endemic area (Indonesia). Serum samples from individuals living in non-endemic area (sub-tropical country) and infants did not show the immunogenic reactions. The objective of this research was to identify two immunogenic proteins, i.e., 31 and 56kDa by using proteomic analysis. In this study, proteomic analysis resulted in identification of 13 proteins and 7 proteins from the 31kDa- and 56kDa-immunogenic protein bands, respectively. Among those proteins, the D7 protein (Arthropode Odorant-Binding Protein, AOBP) was the most abundant in 31-kDa band, and apyrase was the major protein of the 56-kDa band.

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Effect of host plant and immune challenge on the levels of chemosensory and odorant-binding proteins in caterpillar salivary glands. - PubMed - NCBI

Insect Biochem Mol Biol. 2015 Jun;61:34-45. doi: 10.1016/j.ibmb.2015.04.006. Epub 2015 Apr 29.

 

Celorio-Mancera Mde L1, Ytterberg AJ2, Rutishauser D3, Janz N4, Zubarev RA5.

 

Abstract

 

More than half of the proteome from mandibular glands in caterpillars is represented by chemosensory proteins. Based on sequence similarity, these proteins are putative transporters of ligands to gustatory receptors in sensory organs of insects. We sought to determine whether these proteins are inducible by comparing, both qualitatively and quantitatively, the salivary (mandibular and labial) proteomes from caterpillars (Vanessa cardui) reared on different plants and artificial diet containing either bacteria or bacterial cell-walls. We included a treatment where the caterpillars were switched from feeding on artificial diet to plant material at some point in their development. Additionally, we evaluated the degree of overlap between the proteomes in the hemolymph-filled coelom and salivary glands of caterpillars reared on plant material. We found that the quality and quantity of the identified proteins differed clearly between hemolymph-filled coelome, labial and mandibular glands. Our results indicated that even after molting and two-day feeding on a new diet, protein production is affected by the previous food source used by the caterpillar. Candidate proteins involved in chemosensory perception by insects were detected: three chemosensory (CSPs) and two odorant-binding proteins (OBPs). Using the relative amounts of these proteins across tissues and treatments as criteria for their classification, we detected hemolymph- and mandibular gland-specific CSPs and observed that their levels were affected by caterpillar diet. Moreover, we could compare the protein and transcript levels across tissues and treatment for at least one CSP and one OBP. Therefore, we have identified specific isoforms for testing the role of CSPs and OBPs in plant and pathogen recognition. We detected catalase, immune-related protein and serine proteases and their inhibitors in high relative levels in the mandibular glands in comparison to the labial glands. These findings suggest that the mandibular glands of caterpillars may play an important role protecting the caterpillar from oxidative stress, pathogens and aiding in digestion. Contamination with hemolymph proteins during dissection of salivary glands from caterpillars may occur but it is not substantial since the proteomes from hemolymph, mandibular and labial glands were easily discriminated from each other by principal component analysis of proteomic data.

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A surface acoustic wave bio-electronic nose for detection of volatile odorant molecules

Biosens Bioelectron. 2015 May 15;67:516-23. doi: 10.1016/j.bios.2014.09.027. Epub 2014 Sep 18.Di Pietrantonio F, Benetti M, Cannatà D, Verona E, Palla-Papavlu A, Fernández-Pradas JM, Serra P, Staiano M, Varriale A, D'Auria S. Abstract

In this work, a "bio-electronic nose" for vapour phase detection of odorant molecules based on surface acoustic wave (SAW) resonators is presented. The biosensor system is composed of an array of five SAW resonators coated with three types of odorant-binding proteins (OBPs): the wild-type OBP from bovine (wtbOBP), a double-mutant of the OBP from bovine (dmbOBP), and the wild-type OBP from pig (wtpOBP). High resolution deposition of OBPs onto the active area of SAW resonators was implemented through laser-induced forward transfer (LIFT). The resonant frequency shifts of the SAW resonators after the deposition of the biomolecules confirmed the immobilisation of the proteins onto the Al/Au inter-digital transducers (IDTs). In addition, a low increase of insertion losses with a limited degradation of Q-factors is reported. The "bio-electronic nose" fabricated by LIFT is tested in nitrogen upon exposure to separated concentrations of R-(-)-1-octen-3-ol (octenol) and R-(-)-carvone (carvone) vapours. The "bio-electronic nose" showed low detection limits for the tested compounds (i.e. 0.48 ppm for the detection of octenol, and 0.74 ppm for the detection of carvone). In addition, the bio-sensing system was able to discriminate the octenol molecules from the carvone molecules, making it pertinent for the assessment of food contamination by moulds, or for the evaluation of indoor air quality in buildings.

Bernard Offmann's insight:

We are so close to the bio-based electronic nose I ever dreamt ! There is still the issue of odour discrimination & deconvolution in complex mixtures down the road but this work shows it is technologically possible and paves way to it !!

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Expression pattern analysis of odorant-binding proteins in the pea aphid Acyrthosiphon pisum

Insect Sci. 2015 Apr;22(2):220-34. doi: 10.1111/1744-7917.12118. Epub 2014 Apr 29.

 

De Biasio F1, Riviello L, Bruno D, Grimaldi A, Congiu T, Sun YF, Falabella P.

 

Abstract

 

Odorant-binding proteins (OBPs) are soluble proteins mediating chemoreception in insects. In previous research, we investigated the molecular mechanisms adopted by aphids to detect the alarm pheromone (E)-β-farnesene and we found that the recognition of this and structurally related molecules is mediated by OBP3 and OBP7. Here, we show the differential expression patterns of 5 selected OBPs (OBP1, OBP3, OBP6, OBP7, OBP8) obtained performing quantitative RT-PCR and immunolocalization experiments in different body parts of adults and in the 5 developmental instars, including winged and unwinged morphs, of the pea aphid Acyrthosiphon pisum. The results provide an overall picture that allows us to speculate on the relationship between the differential expression of OBPs and their putative function. The expression of OBP3, OBP6, and OBP7 in the antennal sensilla suggests a chemosensory function for these proteins, whereas the constant expression level of OBP8 in all instars could suggest a conserved role. Moreover, OBP1 and OBP3 are also expressed in nonsensory organs. A light and scanning electron microscopy study of sensilla on different body parts of aphid, in particular antennae, legs, mouthparts, and cornicles-cauda, completes this research providing a guide to facilitate the mapping of OBP expression profiles.

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Evidence for trade-offs in detoxification and chemosensation gene signatures in Plutella xylostella

Pest Manag Sci. 2015 Mar;71(3):423-32. doi: 10.1002/ps.3822. Epub 2014 Jun 13.

Bautista MA, Bhandary B, Wijeratne AJ, Michel AP, Hoy CW, Mittapalli O.

 

Abstract

 

BACKGROUND:
Detoxification genes have been associated with insecticide adaptation in the diamondback moth, Plutella xylostella. The link between chemosensation genes and adaptation, however, remains unexplored. To gain a better understanding of the involvement of these genes in insecticide adaptation, the authors exposed lines of P. xylostella to either high uniform (HU) or low heterogeneous (LH) concentrations of permethrin, expecting primarily physiological or behavioral selection respectively. Initially, 454 pyrosequencing was applied, followed by an examination of expression profiles of candidate genes that responded to selection [cytochrome P450 (CYP), glutathione S-transferase (GST), carboxylesterase (CarE), chemosensory protein (CSP) and odorant-binding protein (OBP)] by quantitative PCR in the larvae. Toxicity and behavioral assays were also conducted to document the effects of the two forms of exposure.

 

RESULTS:
Pyrosequencing of the P. xylostella transcriptome from adult heads and third instars produced 198,753 reads with 52,752,486 bases. Quantitative PCR revealed overexpression of CYP4M14, CYP305B1 and CSP8 in HU larvae. OBP13, however, was highest in LH. Larvae from LH and HU lines had up to five- and 752-fold resistance levels respectively, which could be due to overexpression of P450s. However, the behavioral responses of all lines to a series of permethrin concentrations did not vary significantly in any of the generations examined, in spite of the observed upregulation of CSP8 and OBP13.

 

CONCLUSION:
Expression patterns from the target genes provide insights into behavioral and physiological responses to permethrin and suggest a new avenue of research on the role of chemosensation genes in insect adaptation to toxins.

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Chemosensory signals and their receptors in the olfactory neural system.

Neuroscience. 2013 Dec 19;254:45-60. doi: 10.1016/j.neuroscience.2013.08.063. Epub 2013 Sep 14.Ihara S, Yoshikawa K, Touhara K. Abstract

 

Chemical communication is widely used among various organisms to obtain essential information from their environment required for life. Although a large variety of molecules have been shown to act as chemical cues, the molecular and neural basis underlying the behaviors elicited by these molecules has been revealed for only a limited number of molecules. Here, we review the current knowledge regarding the signaling molecules whose flow from receptor to specific behavior has been characterized. Discussing the molecules utilized by mice, insects, and the worm, we focus on how each organism has optimized its reception system to suit its living style. We also highlight how the production of these signaling molecules is regulated, an area in which considerable progress has been recently made.

Bernard Offmann's insight:

Missed that one : re-scooping a not so old review on olfaction and connection to neural system

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Studies on interaction of insect repellent compounds with odorant binding receptor proteins by in silico molecular docking approach.

Abstract

The aim of the study was to identify the interactions between insect repellent compounds and target olfactory proteins. Four compounds, camphor (C10H16O), carvacrol (C10H14O), oleic acid (C18H34O2) and firmotox (C22H28O5) were chosen as ligands. Seven olfactory proteins of insects with PDB IDs: 3K1E, 1QWV, 1TUJ, 1OOF, 2ERB, 3R1O and OBP1 were chosen for docking analysis. Patch dock was used and pymol for visualizing the structures. The interactions of these ligands with few odorant binding proteins showed binding energies. The ligand camphor had showed a binding energy of -136 kcal/mol with OBP1 protein. The ligand carvacrol interacted with 1QWV and 1TUJ proteins with a least binding energy of -117.45 kcal/mol and -21.78 kcal/mol respectively. The ligand oleic acid interacted with 1OOF, 2ERB, 3R1O and OBP1 with least binding energies. Ligand firmotox interacted with OBP1 and showed least binding energies. Three ligands (camphor, oleic acid and firmotox) had one, two, three interactions with a single protein OBP1 of Nilaparvatha lugens (Rice pest). From this in silico study we identified the interaction patterns for insect repellent compounds with the target insect odarant proteins. The results of our study revealed that the chosen ligands showed hydrogen bond interactions with the target olfactory receptor proteins.

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Binding of a fluorescence reporter and a ligand to an odorant-binding protein of the yellow fever mosquito, Aedes aegypti.

By Gabriel M. Leal and Walter S. Leal

In F1000Research.

 

Abstract

Odorant-binding proteins (OBPs), also named pheromone-binding proteins when the odorant is a pheromone, are essential for insect olfaction. They solubilize odorants that reach the port of entry of the olfactory system, the pore tubules in antennae and other olfactory appendages. Then, OBPs transport these hydrophobic compounds through an aqueous sensillar lymph to receptors embedded on dendritic membranes of olfactory receptor neurons. Structures of OBPs from mosquito species have shed new light on the mechanism of transport, although there is considerable debate on how they deliver odorant to receptors. An OBP from the southern house mosquito, Culex quinquefasciatus, binds the hydrophobic moiety of a mosquito oviposition pheromone (MOP) on the edge of its binding cavity. Likewise, it has been demonstrated that the orthologous protein from the malaria mosquito binds the insect repellent DEET on a similar edge of its binding pocket. A high school research project was aimed at testing whether the orthologous protein from the yellow fever mosquito, AaegOBP1, binds DEET and other insect repellents, and MOP was used as a positive control. Binding assays using the fluorescence reporter N-phenyl-1-naphtylamine (NPN) were inconclusive. However, titration of NPN fluorescence emission in AaegOBP1 solution with MOP led to unexpected and intriguing results. Quenching was observed in the initial phase of titration, but addition of higher doses of MOP led to a stepwise increase in fluorescence emission coupled with a blue shift, which can be explained at least in part by formation of MOP micelles to house stray NPN molecules.

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Very nice paper from Walter S. Leal.

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Ligands Binding and Molecular Simulation: the Potential Investigation of a Biosensor Based on an Insect Odorant Binding Protein

Ligands Binding and Molecular Simulation: the Potential Investigation of a Biosensor Based on an Insect Odorant Binding Protein | Odorant Binding Proteins | Scoop.it

Based on mimicking biological olfaction, biosensors have been applied for the detection of various ligands in complex environment, which could represent one of the most promising research fields. In this study, the basic characters of one insect odorant binding protein (OBP) as a biosensor were explored. To explore the molecular recognition process, the tertiary structure of the protein was modeled and the protein-ligand interactions with 1,536,550 chemicals were investigated by the molecular docking. The availability of large amount of recombinant SlitOBP1 overcame the difficulty to obtain biological sensing material. After obtained the purified recombinant protein, the result of fluorescence binding assays proved the candidate protein has good affinities with the majority of the tested chemicals. With the aid of simulation docking, the key conserved amino acids within the binding site were identified and then mutated to alanine. After mutation, the protein-ligand binding characteristics were recorded, and the competitive binding assays were carried out to provide experimental verification. The detailed information on its structure and affinities investigated in this study could allow the design of specific mutants with desired characteristics, which provides a solid base for tailoring OBP for biosensor and provides a role model for screening the other elements in olfactory system for different applications.

 
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Virtual screening on a large scale for OBP1 from Spodoptera litera.

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