I2BC Paris-Saclay

FtrA within the ferrous transport system (Ftr-type) found in pathogenic bacteria is a ferrous iron oxidase able to transform the ferrous ion into its ferric form by reducing a bound copper.

Iron is an essential nutrient in bacteria. Its ferrous form, mostly present in low oxygen and acidic pH environments, can be imported using the specific Ftr-type transport system, which encompasses the conserved FtrABCD system found in pathogenic bacteria such as Bordetella, Brucella and Burkholderia. The non-pathogenicity and versatile metabolism of Rubrivivax gelatinosus make it an ideal model to study the FtrABCD system. Here, we report a new aspect of its regulation and the role of the periplasmic proteins FtrA and FtrB using in vivo and in vitro approaches. We investigated the metal binding mode and redox state of copper and iron to FtrA by crystallography and biophysical methods. An ‘as isolated’ FtrA protein from the bacterial periplasm contained a copper ion (Cu+) identified by electron paramagnetic resonance (EPR). Copper is coordinated by four conserved side chains (His and Met) in the primary metal site. Structural analysis of R. gelatinosus FtrA and FtrA homologues revealed that copper binding induces a rearrangement of the His95 imidazole ring, releasing thereafter space, as well as both Asp45 and Asp92 side chains, for iron binding in the secondary metal site. EPR highlighted that FtrA can oxidize the bound ferrous ion into the ferric form by reducing the bound Cu2+ into Cu+, both metal sites being separated by 7 Å. Finally, we showed that FtrB binds iron and not copper. These results provide new insights into the mechanism of ferrous iron utilization by the conserved FtrABCD iron transporter for which we propose a new functional model.

More information: https://febs.onlinelibrary.wiley.com/doi/10.1111/febs.16476

Contact: Solange Morera <solange.morera@i2bc.paris-saclay.fr >

A study involving the LPSM unveils the mechanism of the human flippase ATP8B1 autoinhibition, as well as its regulation by lipids and phosphorylation. The study provides a better understanding of the impact of flippase mutations responsible for intrahepatic cholestasis on its enzymatic activity.

Biological membranes are dynamic objects whose protein and lipid composition varies over time to ensure many cellular processes. In particular, there is a difference in lipid composition between the two layers of the membrane (lipid asymmetry) which is finely regulated by proteins, including flippases. These proteins catalyze the transport of lipids from the outer (exoplasmic) layer to the inner (cytosolic) layer of the membranes. In humans, mutations in the ATP8B1 flippase are responsible for several forms of intrahepatic cholestasis (familial progressive intrahepatic cholestasis, intrahepatic cholestasis of pregnancy and benign recurrent intrahepatic cholestasis).
Significant efforts are made to understand the lipid transport mechanisms used by ATP8B1 family proteins (P4 ATPase family). In 2019, a European collaboration involving a team from the Protein and Membrane Systems Laboratory (I2BC) unveiled three high-resolution structures (obtained by cryo-electron microscopy) of the yeast homolog (Drs2p) interacting with its Cdc50p subunit. This work revealed the mechanism by which the C-terminus of Drs2p inhibits the activity of the complex and the first steps in the removal of this auto-inhibition by PI4P.
In collaboration with the Universities of Aarhus, Bochum and Copenhagen, the I2BC researchers have this time studied the mechanism of ATP8B1 autoinhibition, as well as its regulation by lipids and phosphorylation. Using cryo-electron microscopy, they established the structure of the ATP8B1-CDC50A complex in an autoinhibited state. They also measured the enzymatic activity of the wild-type protein and of mutants truncated at its N- and/or C-terminus. The researchers show that both ends, and particularly the C-terminal end, play an essential role in the auto-inhibition of the enzyme activity. The efficiency of the inhibition is dependent on the phosphorylation of residue S1223 located in the C-terminal segment. In addition, phosphoinositides, primarily phosphatidylinositol-3,4,5-phosphate (PI(3,4,5)P3), are activators of the enzyme. The use of a synthetic peptide mimicking the C-terminal segment of the protein restores the inhibition of truncated forms of ATP8B1 but differently depending on whether the truncated form contains the N-terminal segment or not. These data suggest a molecular communication between the N- and C-terminal segments in autoinhibition. This result also demonstrates that it is possible to design compounds capable of regulating the activity of the complex. The resolution of the structure of ATP8B1/CDC50A in an autoinhibited state allows to localize the mutations of ATP8B1 responsible for the different forms of intrahepatic cholestasis. The mutations are uniformly distributed over the sequence but most are located in key areas that directly impact the catalytic properties of the enzyme. The presence of the (G/A)(Y/F)AFS motif in the auto-inhibitory C-terminal segment, already identified in other ATPases of the same family and directly involved in the auto-regulation of the enzymatic activity, suggests that this mechanism is widely employed among the flippases of the P4 ATPase family.family and directly involved in the auto-regulation of the enzymatic activity, suggests that this mechanism is widely used among the flippases of the P4 ATPase family.

More information: https://doi.org/10.7554/eLife.75272

Contact: Guillaume Lenoir <guillaume.lenoir@i2bc.paris-saclay.fr >

Caveolin-1β kept its capacity to induce intracellular vesicles in the host when co-expressed with hMGST1 (human microsomal glutathione S-transferase 1) in Spodoptera frugiperda 21 (Sf21) insect cells. Moreover, hMGST1 increased its specific activity.

For a better understanding of membrane proteins cellular role, a detailed knowledge of their function and structure at a molecular level is required. For such studies, especially when combining site-directed mutagenesis and activity test experiments, membrane proteins are efficiently produced using overexpression in heterologous cell systems, among which insect cells. In mammalian cells, caveolin-1, an integral membrane protein of 21 kDa, is the main and characteristic membrane protein component of caveolae membranes. The heterologous expression in Spodoptera frugiperda 21 (Sf21) insect cells of the β isoform of canine caveolin-1 (caveolin-1β), using a baculovirus-based vector, resulted in intracellular vesicles enriched in caveolin-1β. We showed that caveolin-1β kept its capacity to induce intracellular vesicles in the host when co-expressed with hMGST1 (human microsomal glutathione S-transferase 1), and that hMGST1 is in part addressed to these vesicles. Remarkably, a fourfold increase in the amount of active hMGST1 was found in the most enriched membrane fraction, along with an increase of its specific activity by 60% when it was co-expressed with caveolin-1β. Thus, heterologously expressed caveolin-1β was able to induce cytoplasmic vesicles in which a co-expressed exogenous membrane protein is diverted and sequestered, providing a favorable environment for this cargo.

More information: https://doi.org/10.1016/j.bbamem.2022.183922

Contact: Nadège Jamin <nadege.jamin@i2bc.paris-saclay.fr>

ComFC, a protein essential for natural transformation, is a membrane-associated protein with affinity for ssDNA. This dual-specificity allows us to propose that it provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery.

Natural transformation plays a major role in the spreading of antibiotic resistance genes and virulence factors. Whilst bacterial species display specificities in the molecular machineries allowing transforming DNA capture and integration into their genome, the ComFC protein is essential for natural transformation in all Gram- positive and -negative species studied. Despite this, its role remains largely unknown. Here, we show that Helicobacter pylori ComFC is not only involved in DNA transport through the cell membrane, but is required for the handling of the ssDNA once it is delivered into the cytoplasm. ComFC crystal structure revealed the presence of a zinc-finger motif and a putative phosphoribosyl transferase domain, both necessary for the protein's in vivo activity. ComFC is a membrane-associated protein with affinity for single-stranded DNA. Collectively, our results suggest that ComFC provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery.

More information: https://doi.org/10.1038/s41467-022-29494-z

contact: Sophie QUEVILLON-CHERUEL <sophie.quevillon-cheruel@i2bc.paris-saclay.fr>

The necessity to scrutinize biological molecules and their interactions in solution and on the cellular level leads to an increasing demand for specific diagnostic analysis. FRET is ideally suited for multiplexed biosensing because it is rapid and sensitive and allows the use of any fluorescent probe.

The most frequently used technique to detect multiple parameters from a single sample is color multiplexing with different fluorophores. In conventional biosensing approaches, each fluorophore requires a distinct detection channel and excitation wavelength. This drawback can be overcome by Förster resonance energy transfer (FRET) from lanthanide donors to other fluorophore acceptors. The lanthanide multiple and spectrally narrow emission bands over a broad spectral range can overlap with several different acceptors at once, thereby allowing FRET from one donor to multiple acceptors. Their extremely long lifetimes provide two important features: efficient suppression of background from the biological environment using time-gated (TG) detection and detection of specific biomolecules and/or their conformation using temporal multiplexing. Applications range from fundamental analysis of biomolecular interactions and conformations to high-throughput and point-of-care in vitro diagnostics and DNA sequencing to advanced optical encoding, using both liquid and solid samples and in situ, in vitro, and in vivo detection with high sensitivity and selectivity.
In this Account, we discuss recent advances in lanthanide-based TG-FRET for the development and application of advanced immunoassays, nucleic acid sensing, and fluorescence imaging. We highlight the importance of the careful design and combination of different biological, organic, and inorganic molecules and nanomaterials for an adjustable FRET donor–acceptor distance that determines the ultimate performance of the diagnostic assays and conformational sensors in their physiological environment. We conclude by sharing our vision on how progress in the development of new sensing concepts, material combinations, and instrumentation can further advance TG-FRET multiplexing and accelerate its translation into routine clinical practice and the investigation of challenging biological systems.

More information: https://pubs.acs.org/doi/10.1021/acs.accounts.1c00691

Contact: Marcelina Cardoso dos santos  <marcelina.cardoso-dos-santos@i2bc.paris-saclay.fr>

Nature’s trick in conversion of light into chemical energy is revealed when an artificial photo-synthetic model showed evidence of intermediate state pertaining to functionality of electron relay in controlling unidirectional flow and accumulation of charges.

In photosynthesis, Photosystem II is the enzyme that captures sunlight to drive the four-electron, four-proton oxidation of water. It contains a series of co-factors in a defined setup to convoy electrons in a vectorial fashion from the initial locus of light excitation to accumulate charges at the catalytic unit. A pair of Tyr and His amino acids plays a decisive role as relay between the P680 chlorophyll, the primary photooxidant, and the Mn4Ca water oxidizing catalyst (WOC) as it couples the one-photon, one-electron photochemistry of the light absorber to multi-electronic catalysis. A “rocking proton” mechanism operating between these two residues has been identified as a crucial feature of this electron relay. Implementing such functionalities in chemical modular assemblies may help chemists to gain control over the directionality of electron transfer when developing molecular systems for artificial photosynthesis.
Gotico et al. have investigated a set of molecular triads holding a photosensitizer, an imidazole as redox relay, and a monometallic manganese complex as a proxy for a WOC. Time-resolved spectroscopy coupled with the electrochemical properties has permitted to track the formation of an imdazolyl radical, initiated from the photooxidized chromophore, and its subsequent decay connected to oxidation of the Mn(II) site. Comprehensive analysis of the thermodynamic and kinetic parameters reveal the importance of the acid-base properties of this electron relay and highlight the crucial role of reversible proton transfer to allow the system to display a light-induced two-step electron hopping process. This study sets the path for further optimization in the directional electron transfer and charge accumulation for using photons to drive the oxidation of water.

More information here.

Contact person: Winfried LEIBL

The 2nd french congress on integrative structural biology took place on november29th-December 3rd at the Centrale Supelec building, located on the Paris- Saclay plateau. Co-organized by the Association Française de Cristallographie and the Société Française de Biophysique, it brought together over 250 participants of which 63 students.

The program of the event included 13 sessions covering health issues, DNA/RNA world, membrane proteins, intrinsically disordered proteins, macromolecular assemblies. Several round tables allowed discussions about “formation tout au long de la vie”, ” interactions entre académie/industrie”, ” infrastructures” and “la parole scientifique dans l’espace public”. A satellite event on the revolutionnary tool AlphaFold ended up the congress.

Many thanks to the institutional partners (CNRS, CEA, I2BC, ICSN, Ecole Polytechnique, ENS Paris-Saclay, FRISBI, IRRMN, Université Paris-Saclay , Université Paris-Saclay Graduate School Life Sciences and Health, Synchrotron SOLEIL, France-Bioimaging) and industrial partners (Bruker, Cytiva, CytobodX, Dynamic Biosensors, Eurisotop, GenScript, Horiba, Innova-Chem, Jeol, NMR-Bio, Refeyn, Sanofi, Servier, Sptlabtech , Thermofisher, et Twist ) for their support.

Congratulations to Magda Teixeira Nunes and and Luce Dreno who won the best poster prize of the AFC and SFB, respectively!

BSI website

Contact person: Julie Ménétrey

BSI 2021 is presenting special sessions:  

"Science & Société : La parole scientifique dans l'espace public": Many questions have raised by the period we have just passed through concerning the place of scientific speech in public debate, the role of experts (or so-called), interactions between researchers/experts, the media, politicians and the public. This roundtable will seek to shed light on what could/should be the contribution of researchers to public debates and the conditions for this contribution to be effective.

"Session étudiants": UPSaclay students are invited to attend the morning sessions and meet up with researchers. Free but registration required HERE.

"Satellite event - Alpha Fold": With the advent of AlphaFold, the BSI welcomes you to a round table meeting to discuss the impact and opportunity offered by this revolutionary tool. Free but registration required HERE.

Further information and details on how to access the conference location can be found on the BSI 2021 website.

In a study published in European Biophysics Journal, two teams of the B3S department (INTGEN and MIP) with the PIM platform, in collaboration with national and international experts on molecular scale biophysics compare six approches to measure macromolecular interactions in vitro. The results were obtained in the context of a Training School (ARBRE-MOBIEU COST Action) organized in 2019 in our institute.

Biophysical quantification of protein interactions is central to unveil molecular mechanisms of cellular processes. Researchers can choose from a wide panel of biophysical methods, including classical and more novel ones. A real-life proof-of-concept was carried out during an ARBRE-MOBIEU training school held in June 2019 in Gif-sur-Yvette, France (https://mosbio.sciencesconf.org/). Twenty European students benefited from a one-week training with lessons and practical sessions on six complementary approaches: (i) Analytical UltraCentrifugation with or without a Fluorescence Detector System (AUC-FDS), (ii) Isothermal Titration Calorimetry (ITC), (iii) Size Exclusion Chromatography coupled to Multi-Angle Light Scattering (SEC-MALS), (iv) Bio-Layer Interferometry (BLI), (v) MicroScale Thermophoresis (MST) and, (vi) switchSENSE. They implemented all these methods on two examples of macromolecular interactions: firstly, a protein-protein interaction between an artificial alphaRep binder, and its target protein, also an alphaRep; secondly, a protein-DNA interactionbetween a DNA repair complex, Ku70/Ku80 (hereafter called Ku), and its cognate DNA ligand. The students acknowledged that the workshop provided them with a clearer understanding of the advantages and limitations of the different techniques and will help them in the future to choose the approaches that are most relevant or informative for their projects.

More details here

Contact person: Paloma Fernandez Varela

The study reports the CryoEM structures of the core proteins involved in the human NHEJ pathway that repair most DNA double-strand breaks generated in human cells.

Double strand breaks (DSB) are the most toxic DNA lesions in the cell. The Non-homologous end-joining pathway is the main DNA repair pathway in mammals that recognizes, process and ligates DSB. It is initiated by the recognition of DSB by the heterodimer Ku70/80 and the kinase DNA-PKcs that can form a synapse between the two DNA ends of the DSB. Ku70/80 then recruits several enzymatic activities to process and ligate the DNA ends. A team from B3S I2BC collaborates with TL Blundell laboratory (University of Cambridge) to determine cryoEM structure at 4.3Angstrom of the synapse formed by Ku70/80, DNA-PKcs, the ligation complex Ligase4/XRCC4/XLF. This super-complex show a central role of XLF that bridges Ku70/80 and Ligase4/XRCC4 on both side of the synapse. Mutations of the dimer interfaces negatively affect DNA repair.

More details here

Contact person : Jean-Baptiste Charbonnier

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The 3 national infrastructures ProFi, FBI and FRISBI along with the GIS IBiSA proposed a call for a funded access to IBiSA-labelled facilities. This 1st call was a success with 7 projects selected among which one using the Imagerie-Gif facility (@I2BC).

The three national infrastructures ProFi, FranceBioImaging and FRISBI along with the GIS IBiSA proposed a call for a funded access to IBiSA-labelled facilities. The aim was to promote IBiSA facilities networking through transdisciplinary research projects. This 1st call was a success with 26 proposals submitted. Seven projects were selected among which one using using the Imagerie-Gif facility.
One project coordinated by Mireille Bétermier in collaboration with JB Charbonnier was selected. It includes access to the Cytometry platform of Imagerie-Gif at I2BC (France BioImaging), the Proteopole Biophysics platform of Institut Pasteur and the ProteoSeine Mass spectrometry platform of Institut Jacques Monod. The project aims at using approaches from these three IBiSA platforms to integrate complementary data on programmed genome rearrangement and double-strand break repair in Paramecium

 Contact: Julie Ménétrey <julie.menetrey@i2bc.paris-saclay.fr>

The bacterial replicative helicase DnaB is an hexameric ring-shaped ATPase molecular motor that unwinds dsDNA in front of the replisome during replication. Here, we provided a novel structure of the apo-DnaB from Vibrio cholerae which could be an intermediate state in DnaB formation.

To enable chromosomal replication, DNA is unwound by the ATPase molecular motor replicative helicase. The bacterial helicase DnaB is a ring-shaped homo-hexamer whose conformational dynamics are being studied through its different 3D structural states adapted along its functional cycle. Our findings describe a new crystal structure for the apo-DnaB from Vibrio cholerae, forming a planar hexamer with a pseudo-symmetry, constituted by a trimer of dimers in which the CTD domains delimit a triskelion-shaped hole. This hexamer is labile and inactive. We suggest it represents an intermediate state allowing the formation of the active NTP-bound hexamer, from dimers.

More information: http://doi.org/10.1002/1873-3468.14403

Contact: Claire Cargemel <claire.cargemel@i2bc.paris-saclay.fr>

A region of CPAP, a protein regulating the length of the centrioles, is found to have a tubulin binding mode similar to that of bacterial and fungal peptide-like metabolites which inhibit cell division.

Photoactivation of DNA repair enzyme 6-4 photolyase from A. thaliana found to be astonishingly efficient - due to limited ultrafast charge recombination and prevention of solvent access to the terminal tryptophan residue of its electron-transferring chain.

(6–4) Photolyases ((6–4) PLs) are ubiquitous photoenzymes that use the energy of sunlight to catalyze the repair of carcinogenic UV-induced DNA lesions, pyrimidine(6–4)pyrimidone photoproducts. To repair DNA, (6–4) PLs must first undergo so-called photoactivation, in which their excited flavin adenine dinucleotide (FAD) cofactor is reduced in one or two steps to catalytically active FADH− via a chain of three or four conserved tryptophan residues, transiently forming FAD•−/FADH− ⋯ TrpH•+ pairs separated by distances of 15 to 20 Å. Photolyases and related photoreceptors cryptochromes use a plethora of tricks to prevent charge recombination of photoinduced donor–acceptor pairs, such as chain branching and elongation, rapid deprotonation of TrpH•+ or protonation of FAD•−. Here, we address Arabidopsis thaliana (6–4) PL (At64) photoactivation by combining molecular biology, in vivo survival assays, static and time-resolved spectroscopy and computational methods. We conclude that At64 photoactivation is astonishingly efficient compared to related proteins—due to two factors: exceptionally low losses of photoinduced radical pairs through ultrafast recombination and prevention of solvent access to the terminal Trp3H•+, which significantly extends its lifetime. We propose that a highly conserved histidine residue adjacent to the 3rd Trp plays a key role in Trp3H•+ stabilization.

More information: https://www.nature.com/articles/s41598-022-08928-0 

Contact: Pavel MULLER <pavel.muller@i2bc.paris-saclay.fr >

DNA repairing enzymes photolyases are ubiquitous natural catalysts using sunlight to revert cancerogenic chemical changes in DNA caused by UV light. The 3P Team Photobiology, Photosynthesis, Photocatalysis from the Institute of Integrative Biology of the Cell (I2BC) explores the molecular mechanism by which these essential photoenzymes have been repairing DNA since the beginnings of life evolution on Earth.

In their latest work published in the journal ACS Catalysis, the researchers have shown that the repair of the UV-induced lesions called ‘(6-4) photoproducts’ occurs in two successive photoreactions (requiring absorption of two separate photons), each beginning with electron transfer from the excited flavin to the lesion.

Transient absorption spectroscopy (https://www.pluginlabs-universiteparissaclay.fr/fr/entity/a5ad9e5d-53a4-4194-8653-3d8feebfafc8/i2bc-plateforme-de-spectroscopies-electroniques) was used to follow the return of electrons to the flavin after chemical transformations of the lesion. The team was able to dissect the electron return kinetics finalizing the first and the second photoreactions (in ~40 μs and ~200 ns, respectively), corroborating and detailing the two-photon reaction model.

More information: https://doi.org/10.1021/acscatal.2c00492

Authors: Klaus Brettel, Pavel Müller (I2BC) and Junpei Yamamoto (Osaka University). The project was funded by the French National Research Agency (ANR).

Contact: Pavel Müller  <pavel.muller@i2bc.paris-saclay.fr.>

The atomic structure of the nanotubes of Lanreotide, a therapeutic peptide, reveals a complexity that nothing allowed to suspect until now.

Peptide assemblies forming hydrogels or fibrils are used for biomedical applications such as drug and vaccine formulation, cell culture and tissue regeneration. To enable the rational design of these self-assembled peptides, a thorough understanding of the chemical and physico-chemical rules guiding the folding and assembly of these molecules is required. With recent developments in cryo-electron microscopy (cryo-EM), the determination of these structures at the atomic scale has become possible. The study presented makes it possible to reveal by cryo-EM the atomic structure of nanotubes of a therapeutic peptide, Lanreotide. This structure is of a complexity that nothing allowed to suspect until now. These results are published in the journal PNAS.

Functional and versatile nano- and micro-assemblies formed by biological molecules are found at all levels of life, from cellular organelles to complete organisms. Understanding the chemical and physico-chemical determinants guiding the formation of these assemblies is crucial not only to understand the biological processes that they implement but also to mimic nature through the rational design of self-assembled objects that can be used in particular biomedical level. These assemblies result from deterministic chemical interactions and are therefore all potentially predictable. But currently we simply lack the tools to predict how peptides assemble and the potentially polymorphic architectures they can form. To acquire predictive tools based on learning, we need to identify and understand a large number of peptide assembly structures.

Among synthetic peptides forming well-defined nanostructures, the octapeptide Lanreotide has been considered one of the best characterized, both in terms of structure and self-assembly process. Lanreotide is a therapeutic peptide used against acromegaly and certain neuroendocrine cancers. This peptide self-assembles spontaneously in water in the form of nanotubes 24 nm in diameter and extremely long (around one mm), explaining the formation of a hydrogel. This hydrogel allows Lanreotide not only to be protected against chemical degradation but also to be released in a controlled manner over time (more than a month after injection) ensuring its continuous circulation in the blood. The detailed understanding of the chemical and physicochemical rules guiding the assembly of peptides would make it possible to design new controlled-release formulations in which, as in the case of Lanreotide, the drug would be its own formulation. Scientists elucidated the atomic structure of Lanreotide nanotubes obtained at a resolution of 2.5 Å by cryo-EM. This structure reveals a complexity that nothing let suspect in the many previous works and that it would have been impossible to predict by the methods we have today.

The recent and phenomenal success of the artificial intelligence software AlphaFold for the prediction of the tertiary structure of proteins has only been possible thanks to the database of experimentally determined protein atomic structures. However, AlphaFold is not at this stage able to predict peptide folding and assembly. The experimental verification of models at a level of resolution close to the atom must therefore become the norm in this field. This will be an essential step towards the development of reliable predictive methods which will pave the way for the de novo design of peptide materials whose controlled properties will thus find applications in many fields of biology, pharmacy and medicine and may inspire developments in the field of nanotechnology.

I2BC news

Contact person: Maïté Paternostre

Team Interactions and assembly mechanisms of proteins and peptides

Chloé Quignot was awarded "Prix 2021 du Groupe Graphisme et Modélisation Moléculaire (GGMM)" for her PhD thesis in the group "Molecular Assemblies and Genome Integrity".

Chloé Quignot received the GGMM prize for her thesis entitled "Modelling Protein interfaces using evolutionary information", carried out at the I2BC, B3S department, in the Molecular Assemblies and Genome Integrity team and co-supervised by Jessica Andreani and Raphael Guerois. Chloé presented her thesis work at the GGMM-SFCi conference held in Lille in October 2021.
The Graphical and Molecular Modeling Group (GGMM) is a learned society that brings together a large part of the French community whose activity is dedicated to, or involves, the use of molecular modeling. The GGMM prize is awarded every two years for original work in molecular modeling, bioinformatics, chemoinformatics and numerical simulation in the field of structural biology and pharmacology.

Congratulations, Chloé!

more information here.

Thanks to the similarity of in-vitro and in-vivo disorganizing effect of statins on cholesterol-rich membrane microdomains, which constitute the cell entry platforms of the various coronaviruses, including SARS-CoV-2, this host-directed therapeutic approach can be proposed to fight against Covid-19.

The entry of SARS-CoV-2, as well as the other coronaviruses, into its target cells is mediated by cholesterol-rich plasma membrane microdomains, whatever the followed pathway. These «lipid rafts» can be destructured in-vitro by the inhibiting action of statins on the key enzyme of cell cholesterol biosynthesis. As a consequence, raft-dependent signaling platforms are disorganized, leading to various cellular effects. In clinics, beyond the classical hypocholesterolemic effect of statins, these drugs can induce various «pleiotropic effects» (anti-inflammatory, immunomodulation, vascular protection...) that are mediated by such signaling platforms. This indicates that statins, administered under clinical situations, are able to in-vivo perturb cholesterol-rich membrane domains, which should include those involved in various pathogenic agents, including SARS-CoV-2, entry platforms. We thus propose statins as a new repurposing strategy against Covid-19, taking into account they are well-known, widely-used safe drugs (used for long-term prevention for high-risk cardio-vascular patients), administered per os, cheap, and overall avoiding any risk of encountering treatment resistances due to viral mutations because it is a «host-directed» therapeutic approach [Orlowski et al, Biochimie 189, 51 (2021)]. It remains to test experimentally this hypothesis.

Contact person: Stephane Orlowski

The interaction between BRCA2 and its interactor HSF2BP, both required for meiotic recombination, is defined structurally, revealing that a repeat in BRCA2 binds two HSF2BP units, increasing the affinity up to the nanomolar range. Unexpectedly, this repeat is not essential for mouse meiosis.

BRCA2 and its interactors are required for meiotic homologous recombination (HR) and fertility. Loss of HSF2BP, a BRCA2 interactor, disrupts HR during spermatogenesis. We test the model postulating that HSF2BP localizes BRCA2 to meiotic HR sites, by solving the crystal structure of the BRCA2 fragment in complex with dimeric armadillo domain (ARM) of HSF2BP and disrupting this interaction in a mouse model. This reveals a repeated 23 amino acid motif in BRCA2, each binding the same conserved surface of one ARM domain. In the complex, two BRCA2 fragments hold together two ARM dimers, through a large interface responsible for the nanomolar affinity — the strongest interaction involving BRCA2 measured so far. Deleting exon 12, encoding the first repeat, from mBrca2 disrupts BRCA2 binding to HSF2BP, but does not phenocopy HSF2BP loss. Thus, results herein suggest that the high-affinity oligomerization-inducing BRCA2-HSF2BP interaction is not required for RAD51 and DMC1 recombinase localization in meiotic HR.

More details here

Contact person : Sophie Zinn

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