Multiplexed assays of variant effects (MAVEs) make it possible to measure the functional impact of all possible single amino acid residue substitutions in a protein in a single experiment. Combination of variant effect data from several such experiments provides the opportunity to conduct large-scale analyses of variant effect scores measured across proteins, but can be complicated by variations in the phenotypes that are probed across experiments. Thus, using variant effect datasets obtained with similar MAVE techniques can help reveal general rules governing the effects of amino acid variation for a single molecular phenotype. In this work, we accordingly combined data from six individual variant abundance by massively parallel sequencing (VAMP-seq) experiments and analysed a total of 31,614 variant effect scores reporting solely on the impact of single amino acid residue substitutions on the cellular abundance of proteins. Using our combined variant effect dataset, we derived and analysed a collection of amino acid substitution matrices describing the average impact on cellular abundance of all residue substitution types in different structural environments. We found that the substitution matrices predict the cellular abundance of protein variants with surprisingly high accuracy when given structural information only in the form of whether a residue is buried or exposed. We thus propose our substitution matrix-based predictions as strong baselines for future abundance model development.

Integral membrane proteins comprise at least a quarter of every proteome. To fold and function properly, these proteins must insert into the correct membrane with the proper topology and orientation. Although their transmembrane helices are chemically compatible with the bilayer, insertion inside cells is not a simple spontaneous event. It must occur in a crowded environment, at the correct membrane, and it often involves challenges such as transferring hydrophilic segments across the bilayer or accommodating helices that are only marginally compatible with it. Cells therefore rely on dedicated systems that direct membrane proteins to the membrane, mediate their insertion, and monitor the process to ensure that it occurs correctly. This review outlines the principles that govern membrane protein insertion in cells and explains how transmembrane sequence features interact with the machineries that mediate their entry into the bilayer. We highlight the major insertion systems of bacteria and eukaryotes and the auxiliary factors that support them, and describe how these pathways accommodate the broad range of membrane protein architectures found in cells, from single-pass proteins to complex multispanning transporters. We also discuss how cells maintain accuracy when insertion fails, through mechanisms that detect and resolve misinsertion. Together, these concepts present membrane protein insertion as a coordinated, adaptable, and safeguarded process, shaped by the interplay between sequence properties, membrane environments, and the machinery responsible for building the membrane proteome.

Microalgae, as efficient photosynthetic microorganisms, hold great potential for solar-driven carbon fixation and sustainable biomanufacturing. However, their performance is limited by spectral mismatch, inefficient electron transport, and diffusion-limited CO2 assimilation. Recent developments in microalgae-based semiartificial photosynthetic systems (SAPSs) combine living algal cells with engineered abiotic components to address these challenges without in vitro photosynthesis reconstruction. In SAPSs, microalgae provide carbon fixation, metabolic flexibility, and regulatory adaptability, while functional materials optimize photon utilization, electron transfer, CO2 concentration, and environmental robustness. This review critically examines the biological foundations of microalgae–material integration, strategies for optical enhancement, electron-transfer regulation, CO2 concentration, and stress mitigation. It discusses applications in solar fuel production, biomanufacturing, environmental remediation, and biohybrid microrobots. Despite advancements, key challenges remain, such as energy coupling at bio-abiotic interfaces, lack of standardized performance metrics, long-term stability, and sustainability concerns with nanomaterials. Future SAPS progress will require an integrated approach combining materials science, synthetic biology, and life-cycle assessment (LCA) to scale laboratory efficiencies into environmentally sustainable technologies for carbon-neutral energy conversion and biomanufacturing.