Biology subjects

Rozovsky, S.

Publications and source records attributed to Rozovsky, S..

4 recordsLinked to original sources

bioRxiv2026

Selenoprotein S plays role in translation and membrane protein biogenesis

Human selenoprotein S (selenos) is part of the integrated cellular stress response and linked to protein quality control and signaling pathways. Consequently, genetic polymorphisms of selenos are associated with increased risk for diabetes, dyslipidemia, and cardiovascular diseases. Determining the specific roles of selenos in these cellular pathways and diseases has been challenging, as selenos associates with a wide range of protein complexes. Thus, to map the cellular functions of selenos and uncover their interconnections, we used affinity purification and in vivo crosslinking to stabilize transient protein interactions, followed by proteomics to record the resulting selenos interactome. Through mapping of selenos protein partners, we found evidence that selenos associates with complexes responsible for the insertion of membrane proteins into the ER bilayer and their connected quality control components. Furthermore, selenos is also part of metabolic, trafficking, and mitochondrial pathways. Notably, proteins involved in translation preferentially associate with selenos when its C-terminal intrinsically disordered segment containing the redox-active motif is accessible. Together, these results identify the C-terminal redox loop of selenos as a central interaction hub connecting translation with ER membrane protein biogenesis and quality control.

biochemistry↗

bioRxiv2024

CryoCycle your grids: Plunge vitrifying and reusing clipped grids to advance cryoEM democratization

CryoEM democratization is hampered by access to costly plunge-freezing supplies. We introduce methods, called CryoCycle, for reliably blotting, vitrifying, and reusing clipped cryoEM grids. We demonstrate that vitreous ice may be produced by plunging clipped grids with purified proteins into liquid ethane and that clipped grids may be reused several times for different protein samples. Furthermore, we demonstrate the vitrification of thin areas of cells prepared on gold-coated, pre-clipped grids.

molecular biology↗

bioRxiv2021

The Unconventional Self-Cleavage of Selenoprotein K

Through known association with other proteins, human selenoprotein K (selenok) is currently implicated in the palmitoylation of proteins, degradation of misfolded proteins, innate immune response, and the life cycle of SARS-CoV-2 virus. However, neither the catalytic function of selenoks selenocysteine (Sec), which, curiously, resides in an intrinsically disordered protein segment nor selenoks specific role in these pathways are known to date. This report casts these questions in a new light as it describes that selenok is able -both in vitro and in vivo- to cleave some of its own peptide bonds. The cleavages not only release selenok segments that contain its reactive Sec, but as the specific cleavage sites were identified, they proved to cluster tightly near sites through which selenok interacts with protein partners. Furthermore, it is shown that selenoks cleavage activity is neither restricted to itself nor promiscuous but selectively extends to at least one of its protein partners. Together, selenoks cleavage ability and its features have all hallmarks of a regulatory mechanism that could play a central role in selenoks associations with other proteins and its cellular functions overall.

biochemistry↗

bioRxiv2018

Fe oxidation by a fused cytochrome-porin common to diverse Fe-oxidizing bacteria

Iron (Fe) oxidation is one of Earths major biogeochemical processes, key to weathering, soil formation, water quality, and corrosion. However, our understanding of microbial contribution is limited by incomplete knowledge of microbial iron oxidation mechanisms, particularly in neutrophilic iron-oxidizers. The genomes of many, diverse iron-oxidizers encode a homolog to an outer-membrane cytochrome (Cyc2) shown to oxidize iron in two acidophiles. Phylogenetic analyses show Cyc2 sequences from neutrophiles cluster together, suggesting a common function, though this function has not been verified in these organisms. Therefore, we investigated the iron oxidase function of heterologously expressed Cyc2 from a neutrophilic iron-oxidizer Mariprofundus ferrooxydans PV-1. Cyc2PV-1 is capable of oxidizing iron, and its redox potential is 208 {+/-} 20 mV, consistent with the ability to accept electrons from Fe2+ at neutral pH. These results support the hypothesis that Cyc2 functions as an iron oxidase in neutrophilic iron-oxidizing organisms. Sequence analysis and modeling reveal the entire Cyc2 family share a unique fused cytochrome-porin structure, with a defining consensus motif in the cytochrome region. Based on structural analyses, we predict that the monoheme cytochrome Cyc2 specifically oxidizes dissolved Fe2+, in contrast to multiheme iron oxidases, which may oxidize solid Fe(II). With our results, there is now functional validation for diverse representatives of Cyc2 sequences. We present a comprehensive Cyc2 phylogenetic tree and offer a roadmap for identifying cyc2/Cyc2 homologs and interpreting their function. The occurrence of cyc2 in many genomes beyond known iron-oxidizers presents the possibility that microbial iron oxidation may be a widespread metabolism. ImportanceIron is practically ubiquitous across Earths environments, central to both life and geochemical processes, which depend heavily on the redox state of iron. Although iron oxidation, or "rusting," can occur abiotically at near neutral pH, we find neutrophilic iron-oxidizing bacteria (FeOB) are widespread, including in aquifers, sediments, hydrothermal vents, pipes, and water treatment systems. FeOB produce highly reactive Fe(III) oxyhydroxides that bind a variety of nutrients and toxins, thus these microbes are likely a controlling force in iron and other biogeochemical cycles. There has been mounting evidence that Cyc2 functions as an iron oxidase in neutrophiles, but definitive proof of its function has long eluded us. This work provides conclusive biochemical evidence of iron oxidation by Cyc2 from neutrophiles. Cyc2 is common to a wide variety of iron-oxidizers, including acidophilic and phototrophic iron-oxidizers, suggesting that this fused cytochrome-porin structure is especially well-adapted for iron oxidation.

microbiology↗