Biology subjects

Vlasov, A.

Publications and source records attributed to Vlasov, A..

6 recordsLinked to original sources

bioRxiv2026

Structure of a dodecameric double-ferritin-fold protein from an Asgard archaeon

Ferritins are ubiquitous iron homeostasis proteins found across the tree of life that form conserved 24-subunit cages with octahedral (4-3-2) symmetry. New types of ferritins and ferritin-like proteins are being continuously discovered, such as mini-bacterioferritins, which form smaller shells of 12 subunits, and double-ferritin-fold proteins, which act as ferroxidases but do not form shells. Here, we describe double-ferritin-fold proteins from Asgard archaea, dubbed dFTNs, and determine Cryo-EM structure of a representative from Candidatus Heimdallarchaeum endolithica. The protein forms a dodecameric shell with tetrahedral (2-3) symmetry. N-terminal (NTD) and C-terminal (CTD) domains are bridged by an ordered linker and are related by two-fold rotational pseudosymmetry. C-terminal -helix (helix E) that forms the four-fold channel in classic ferritins is repositioned to be the helix 2 out of 5 ferritin domain -helices in dFTN, with two such helices from NTD and two helices from CTD forming a pseudo-four-fold symmetry structural element. Four three-fold channels are formed by NTDs, and four other such channels are formed by CTDs. The overall arrangement of dFTN ferritin domains is similar to that of protomers in classic ferritin shells. Altogether, our findings expand the range of known ferritin family proteins and provide insight into Asgard archaea iron metabolism.

biophysics↗

bioRxiv2025

Topological adaptation of heliorhodopsins enables exogenous second-antenna acquisition in monoderm phototrophs

Heliorhodopsins (HeRs), the third rhodopsin family, are characterized by inverted membrane topology and confinement to monoderm organisms, yet their biological meaning has so far remained a mystery. We report the first crystal structure of a eukaryotic HeR, supported by structural modeling and comparative analyses across all domains of life. A conserved carotenoid-binding site, reminiscent of secondary antennae in some microbial rhodopsins, is identified and found to be common among HeRs. We show that inverted topology allows recruitment of exogenous xanthophylls, inaccessible in diderm cells, explaining HeRs distinctive orientation and distribution. These findings reveal a previously unrecognized light-harvesting mechanism of HeRs, expand the known repertoire of microbial phototrophy, and suggest evolutionary constraints linking membrane topology to environmental metabolite accessibility.

biochemistry↗

bioRxiv2025

Structural and Functional Characterization of Encapsulin-Targeted Double Ferritin Fold Ferroxidases

Ferritins are a widespread family of proteins involved in iron homeostasis. While classic ferritins consist of four -helices and form 24-meric nanocages, related ferritin-like proteins display other types of assemblies and sometimes lack any iron storage capacity. Here, by analyzing the available genomic data, we identify a family of double ferritin-like proteins (DFLPs) composed of two four-helical domains, which arose by duplication of a ferritin fold protein. We characterize representative DFLPs from Thermocrinis minervae and Caldanaerovirga acetigignens, TmDFLP and CaDFLP, and show that they form homodimers and bind heme. We determine the X-ray structure of TmDFLP and demonstrate its ferroxidase activity. Furthermore, we show that some DFLPs, including TmDFLP and CaDFLP, are highly likely to be targeted into encapsulin shells. Our work expands the range of known iron metabolism systems and highlights the power of genome mining for discovery of new proteins. Graphical Abstract for Table of Contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=64 SRC="FIGDIR/small/676036v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@72e6b0org.highwire.dtl.DTLVardef@18752fforg.highwire.dtl.DTLVardef@15a02e7org.highwire.dtl.DTLVardef@74cd02_HPS_FORMAT_FIGEXP M_FIG C_FIG A family of double ferritin-like proteins (DFLPs) composed of two four-helical domains is described and investigated. DFLPs are shown to form homodimers, bind heme, possess diiron sites and display ferroxidase activity. Some DFLPs are shown to be targeted to encapsulin shells as core or secondary cargo, thus representing a new type of iron metabolism systems.

biochemistry↗

bioRxiv2025

A new family of small ArdA proteins reveals an antirestriction activity.

Antirestriction proteins are known to protect mobile genetic elements from the hosts restriction-modification (RM) systems. In our study, we identified a new family of small proteins, which we named sArdA The sArdA proteins are homologous to DNA-mimicking ArdA proteins but differ in size, being approximately one-third the length of full ArdAs. Moreover, sArdA family contains two subgroups, one of which is structurally similar to the N-terminal end of ArdA, while the other one - to the C-terminal end. Phylogenetic analysis demonstrated that genes encoding these proteins evolved into evolutionarily stable subfamilies, named sArdN and sArdC, respectively. Alphafold structure prediction of sArdA interaction with RM systems revealed four states of EcoKI, which differ the angle between its two M-subunits while interacting with different agents. Interestingly, both sArdN and sArdC triggered the same intermediate closed state of EcoKI indicating the possible new interaction pathways of Ards with RM systems. For phenotypic studies in Escherichia coli cells, we cloned the sardN gene from the chromosome of Corynebacterium pilbarense and the sardC gene from Lactococcus cremoris. Both genes were shown to protect {lambda} phage DNA from restriction by the type I RM system. However, they revealed specificity to different restriction-modification systems. Specifically, sArdC was more effective against EcoR124II, whereas sArdN was more potent against EcoKI. Furthermore, both genes demonstrated high antimethylation activity against EcoKI. Our current findings suggest the idea that binding specificity of DNA-mimicking proteins to their targets could also be achieved by very short proteins.

molecular biology↗

bioRxiv2024

High-throughput algorithm predicts F-Type ATP synthase rotor ring stoichiometries of 8 to 27 protomers

ATP synthases are large enzymes present in every living cell. They consist of a transmembrane and a soluble domain, each comprising multiple subunits. The transmembrane part contains an oligomeric rotor ring (c-ring), whose stoichiometry defines the ratio between the number of synthesized ATP molecules and the number of ions transported through the membrane. Currently, c-rings of F-Type ATP synthases consisting of 8 to 17 (except 16) subunits have been experimentally demonstrated. Here, we present an easy-to-use high-throughput computational approach based on AlphaFold that allows us to estimate the stoichiometry of all homooligomeric c-rings, whose sequences are present in genomic databases. We validate the approach on the available experimental data, obtaining the correlation as high as 0.94 for the reference data set, and use it to predict the existence of c-rings with stoichiometry varying from 8 to 27. We then conduct molecular dynamics simulations of two c-rings with stoichiometry above 17 to corroborate the machine learning-based predictions. Our work strongly suggests existence of rotor rings with previously undescribed high stoichiometry in natural organisms and highlights the utility of AlphaFold-based approaches for studying homooligomeric proteins.

bioinformatics↗

bioRxiv2023

Basal MET Phosphorylation is an Indicator of Hepatocyte Dysregulation in Liver Disease

Chronic liver diseases are worldwide on the rise. Due to the rapidly increasing incidence, in particular in Western countries, Non-alcoholic fatty liver disease (NAFLD) is gaining importance as the disease can develop into hepatocellular carcinoma. Lipid accumulation in hepatocytes has been identified as the characteristic structural change in NAFLD development, but molecular mechanisms responsible for disease progression remained unresolved. Here, we uncover in primary hepatocytes from a preclinical model fed with a Western diet (WD) a strong downregulation of the PI3K-AKT pathway and an upregulation of the MAPK pathway. Dynamic pathway modeling of hepatocyte growth factor (HGF) signal transduction combined with global proteomics identifies that an elevated basal MET phosphorylation rate is the main driver of altered signaling leading to increased proliferation of WD-hepatocytes. Model-adaptation to patient-derived hepatocytes reveal patient-specific variability in basal MET phosphorylation, which correlates with patient outcome after liver surgery. Thus, dysregulated basal MET phosphorylation could be an indicator for the health status of the liver and thereby inform on the risk of a patient to suffer from liver failure after surgery.

systems biology↗