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Ефремов Роман Гербертович

Московский институт электроники и математики им. А.Н. Тихонова

Профиль на hse.ru ↗ тел.: +7 (495) 916-88-76 | 15129 | +7 (903) 743-16-56
Публикаций
127
Языков
2
Наград
5
Конференций
3
Профиль Публикации (127) Курсы (4)

Профессиональные интересы

Вычислительная биологиякомпьютерная биологиямолекулярное моделированиеструктура и динамика биомолекулбиофизика

Должности

  • Профессор — Московский институт электроники и математики им. А.Н. Тихонова, Департамент прикладной математики

Био

  • · Начал работать в НИУ ВШЭ в 2013 году.
  • · Научно-педагогический стаж: 42 года.

Образование

  • 2007 · Ученое звание: Профессор
  • 2000 · Доктор физико-математических наук
  • 1986 · Кандидат физико-математических наук
  • 1983 · Специалитет: Московский инженерно-физический институт, специальность «Дозиметрия и защита», квалификация «Инженер-физик»

Награды и поощрения

  • · Участие в научных советах и обществах: член Ученого Совета ИБХ РАН; член трех специализированных диссертационных советов (ИБХ РАН, МГУ, ГУ НИИ БМХ РАМН); член Американского химического общества; член Биофизического общества (США).
  • · Надбавка за публикацию в журнале из Списка А (и приравненном к нему научном издании) (2025–2026, 2024–2025, 2023–2024)
  • · Надбавка за публикацию в международном рецензируемом научном издании (2022–2023, 2021–2022, 2019–2021)
  • · Надбавка за статью в зарубежном рецензируемом журнале (2014–2016)
  • · Надбавка за статью в зарубежном рецензируемом научном издании (2016–2018)

Гранты и проекты

  • 2016 · Грант Российского научного фонда «Компьютерный анализ структурно-функциональных аспектов олигомеризации трансмембранных доменов рецепторов сигнальных систем клетки», 2014-2016 гг., руководитель.
  • 2016 · Грант Российского научного фонда «Молекулярные технологии управления нейросигнализацией», 2014-2016 гг., отв. соисполнитель.
  • 2017 · Грант Программы Президиума РАН «Молекулярная и клеточная биология», тема: «Молекулярное моделирование пептидов и белков в мембранах как фундаментальная основа для рационального конструирования новых биологически активных соединений», 2013-2017 гг., руководитель.
  • 2014 · Грант Программы Президиума РАН № 27 «Основы фундаментальных исследований нанотехнологий и наноматериалов», тема: «Новые вычислительные технологии мультимасштабного моделирования мезоскопических биомембранных систем: от понимания фундаментальных принципов структурно-динамического поведения – к созданию наноструктур для биомедицинских приложений», 2012-2014 гг., руководитель.
  • 2015 · Грант РФФИ «Коллективные молекулярные движения, кластеры и флуктуации в гидратированных липидных бислоях и их роль в структурно-динамическом поведении клеточных мембран», 2013-2015 гг., руководитель.
  • 2018 · Грант РФФИ «Клеточные мембраны как стохастические динамические системы: от атомистического моделирования – к рациональному конструированию новых мембранных материалов», 2016-2018 гг., руководитель.

Конференции (3)

Показать все
  • · 2016: Актуальные вопросы биологической физики и химии БФФХ-2016 (Севастополь). Доклад: Оценка влияния среды на димеризацию трансмембранных доменов гликофорина А в компьютерном эксперименте
  • · 2016: Khujand Symposium on Computational Materials and Biological Sciences 2016 (Худжанд). Доклад: Helix-helix interactions in membranes: focus on lipids
  • · 2014: Dushanbe Symposium on Computational Materials and Biological Sciences DSCMBS-2014 (Душанбе). Доклад: The adaptable lipid matrix promotes transmembrane helices association in membranes

Идентификаторы исследователя

Публикации (127)

Molecular Dynamics of DHHC20 Acyltransferase Suggests Principles of Lipid and Protein Substrate Selectivity

2022 · ARTICLE · en

Lipid modification of viral proteins with fatty acids of different lengths (S-acylation) is crucial for virus pathogenesis. The reaction is catalyzed by members of the DHHC family and proceeds in two steps: the autoacylation is followed by the acyl chain transfer onto protein substrates. The crystal structure of human DHHC20 (hDHHC20), an enzyme involved in the acylation of S-protein of SARS-CoV-2, revealed that the acyl chain may be inserted into a hydrophobic cavity formed by four transmembrane (TM) α-helices. To test this model, we used molecular dynamics of membrane-embedded hDHHC20 and its mutants either in the absence or presence of various acyl-CoAs. We found that among a range of acyl chain lengths probed only C16 adopts a conformation suitable for hDHHC20 autoacylation. This specificity is altered if the small or bulky residues at the cavity’s ceiling are exchanged, e.g., the V185G mutant obtains strong preferences for binding C18. Surprisingly, an unusual hydrophilic ridge was found in TM helix 4 of hDHHC20, and the responsive hydrophilic patch supposedly involved in association was found in the 3D model of the S-protein TM-domain trimer. Finally, the exchange of critical Thr and Ser residues in the spike led to a significant decrease in its S-acylation. Our data allow further development of peptide/lipid-based inhibitors of hDHHC20 that might impede replication of Corona- and other enveloped viruses.

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Differences in medium-induced conformational plasticity presumably underlie different cytotoxic activity of ricin and viscumin

2022 · ARTICLE · en

Structurally similar catalytic subunits A of ricin (RTA) and viscumin (MLA) exhibit cytotoxic activity through ribosome inactivation. Ricin is more cytotoxic than viscumin, although the molecular cause of this is still poorly understood. To shed more light on this problem, we used a combined biochemical / molecular modeling approach to assess the possible relationship between the activity of toxins and their structural/dynamic properties. Based on bioassay measurements, it was suggested that the differences in activity are associated with the ability of RTA and MLA to undergo structural/hydrophobic rearrangements when trafficking through the endoplasmic reticulum (ER) membrane. Molecular dynamics simulations and surface hydrophobicity mapping of both proteins in different media showed that RTA rearranges its structure in a membrane-like environment much more efficiently than MLA. The hydrophobic organization of their refolded states is also drastically different. We assume that the higher conformational plasticity of RTA is favorable for the ER-mediated translocation pathway, which leads to a higher rate of the toxin penetration into the cytoplasm.

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Variability in the Spatial Structure of the Central Loop in Cobra Cytotoxins Revealed by X-ray Analysis and Molecular Modeling

2022 · ARTICLE · en

Cobra cytotoxins (CTs) belong to the three-fingered protein family and possess membrane activity. Here, we studied cytotoxin 13 from Naja naja cobra venom (CT13Nn). For the first time, a spatial model of CT13Nn with both “water” and “membrane” conformations of the central loop (loop-2) were determined by X-ray crystallography. The “water” conformation of the loop was frequently observed. It was similar to the structure of loop-2 of numerous CTs, determined by either NMR spectroscopy in aqueous solution, or the X-ray method. The “membrane” conformation is rare one and, to date has only been observed by NMR for a single cytotoxin 1 from N. oxiana (CT1No) in detergent micelle. Both CT13Nn and CT1No are S-type CTs. Membrane-binding of these CTs probably involves an additional step—the conformational transformation of the loop-2. To confirm this suggestion, we conducted molecular dynamics simulations of both CT1No and CT13Nn in the Highly Mimetic Membrane Model of palmitoiloleoylphosphatidylglycerol, starting with their “water” NMR models. We found that the both toxins transform their “water” conformation of loop-2 into the “membrane” one during the insertion process. This supports the hypothesis that the S-type CTs, unlike their P-type counterparts, require conformational adaptation of loop-2 during interaction with lipid membranes.

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Structure-based rational design of an enhanced fluorogen-activating protein for fluorogens based on GFP chromophore

2022 · ARTICLE · en

“Fluorescence-Activating and absorption-Shifting Tag” (FAST) is a well-studied fluorogenactivating protein with high brightness and low size, able to activate a wide range of fluorogens. This makes FAST a promising target for both protein and fluorogen optimization. Here, we describe the structure-based rational design of the enhanced FAST mutants, optimized for the N871b fluorogen. Using the spatial structure of the FAST/N871b complex, NMR relaxation analysis, and computer simulations, we identify the mobile regions in the complex and suggest mutations that could stabilize both the protein and the ligand. Two of our mutants appear brighter than the wild-type FAST, and these mutants provide up to 35% enhancement for several other fluorogens of similar structure, both in vitro and in vivo. Analysis of the mutants by NMR reveals that brighter mutants demonstrate the highest stability and lowest length of intermolecular H-bonds. Computer simulations provide the structural basis for such stabilization.

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A uniquely stable trimeric model of SARS-CoV-2 spike transmembrane domain

2022 · ARTICLE · en

Understanding fusion mechanisms employed by SARS-CoV-2 spike protein entails realistic transmembrane domain (TMD) models, while no reliable approaches towards predicting the 3D structure of transmembrane (TM) trimers exist. Here, we propose a comprehensive computational framework to model the spike TMD only based on its primary structure. We performed amino acid sequence pattern matching and compared the molecular hydrophobicity potential (MHP) distribution on the helix surface against TM homotrimers with known 3D structures and selected an appropriate template for homology modeling. We then iteratively built a model of spike TMD, adjusting “dynamic MHP portraits” and residue variability motifs. The stability of this model, with and without palmitoyl modifications downstream of the TMD, and several alternative configurations (including a recent NMR structure), was tested in all-atom molecular dynamics simulations in a POPC bilayer mimicking the viral envelope. Our model demonstrated unique stability under the conditions applied and conforms to known basic principles of TM helix packing. The original computational framework looks promising and could potentially be employed in the construction of 3D models of TM trimers for a wide range of membrane proteins.

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The Mechanism of Selective Recognition of Lipid Substrate by hDHHC20 Enzyme

2022 · ARTICLE · en

S-acylation is a post-translational linkage of long chain fatty acids to cysteines, playing a key role in normal physiology and disease. In human cells, the reaction is catalyzed by a family of 23 membrane DHHC-acyltransferases (carrying an Asp-His-His-Cys catalytic motif) in two stages: (1) acyl-CoA-mediated autoacylation of the enzyme; and (2) further transfer of the acyl chain to a protein substrate. Despite the availability of a 3D-structure of human acyltransferase (hDHHC20), the molecular aspects of lipid selectivity of DHHC-acyltransferases remain unclear. In this paper, using molecular dynamics (MD) simulations, we studied membrane-bound hDHHC20 right before the acylation by C12-, C14-, C16-, C18-, and C20-CoA substrates. We found that: (1) regardless of the chain length, its terminal methyl group always reaches the “ceiling” of the enzyme’s cavity; (2) only for C16, an optimal “reactivity” (assessed by a simple geometric criterion) permits the autoacylation; (3) in MD, some key interactions between an acyl-CoA and a protein differ from those in the reference crystal structure of the C16-CoA-hDHHS20 mutant complex (probably, because this structure corresponds to a non-native dimer). These features of specific recognition of full-size acyl-CoA substrates support our previous hypothesis of “geometric and physicochemical selectivity” derived for simplified acyl-CoA analogues.

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Stepwise insertion of cobra cardiotoxin CT2 into a lipid bilayer occurs as an interplay of protein and membrane “dynamic molecular portraits”

2021 · ARTICLE · en

For many peripheral membrane-binding proteins (MBPs), especially β-structural ones, the precise molecular mechanisms of membrane insertion remain unclear. In most cases, only the terminal water-soluble and membrane-bound states have been elucidated, whereas potential functionally important intermediate stages are still not understood in sufficient detail. In this study we present one of the first successful attempts to describe step-by-step embedding of the MBP cardiotoxin 2 (CT2) from cobra N. oxiana venom into a lipid bilayer at the atomistic level. CT2 possesses a highly conservative and rigid b-structured three-finger fold shared by many other exogenous and endogenous proteins performing a wide variety of functions. Incorporation of CT2 into the lipid bilayer was analyzed via a 2-μs all-atom molecular dynamics (MD) simulation without restraints. This process was shown to occur over a number of distinct steps, while the geometry of initial membrane attachment drastically differs from the final equilibrated state. In the latter one, the hydrophobic platform (“bottom”) formed by the tips of the three loops is deeply buried into the lipid bilayer. This agrees well with the NMR data obtained earlier for CT2 in detergent micelles. However, the bottom is too bulky to insert itself into the membrane at once. Instead, gradual immersion of CT2 initiated by the loop-1 was observed. This initial binding stage was also demonstrated in a series of MD runs with varying starting orientations of the toxin with respect to the bilayer surface. Apart from non-specific long-range electrostatic attraction and hydrophobic match/mismatch factor, several specific lipid binding sites were identified in CT2. They were shown to promote membrane insertion by engaging in strong interactions with lipid head groups, fine-tuning the toxin-membrane accommodation. We therefore propose that the toxin insertion relies on an interplay of nonspecific and specific interactions, which are determined by the “dynamic molecular portraits” of the two players, the protein and the membrane. The proposed model does not require protein oligomerization for membrane insertion and can be further employed to design MBPs with predetermined properties with regard to particular membrane targets.

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Potassium channel blocker crafted by ɑ-hairpinin scaffold engineering

2021 · ARTICLE · en

ɑ-Hairpinins are a family of plant defense peptides with a common fold presenting two short ɑ-helices stabilized by two invariant S–S-bridges. We have shown previously that substitution of just two amino acid residues in a wheat ɑ-hairpinin Tk-AMP-X2 leads to Tk-hefu-2 that features specific affinity to voltage-gated potassium channels KV1.3. Here, we utilize a combined molecular modeling approach based on molecular dynamics simulations and Protein Surface Topography technique to improve the affinity of Tk-hefu-2 to KV1.3 while preserving its specificity. An important advance of this work compared to our previous studies is transition from the analysis of various physico-chemical properties of an isolated toxin molecule to its consideration in complex with its target, a membrane-bound ion channel. As a result, a panel of computationally designed Tk-hefu-2 derivatives was synthesized and tested against KV1.3. The most active mutant Tk-hefu-10 showed an IC50 of ∼150 nM being >10 times more active than Tk-hefu-2 and >200 times more active than the original Tk-hefu. We conclude that ɑ-hairpinins provide an attractive disulfide-stabilized scaffold for the rational design of ion channel inhibitors. Furthermore, success rate can be considerably increased by the proposed “target-based” iterative strategy of molecular design.

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libxtc: An efficient library for reading XTC-compressed MD trajectory data

2021 · ARTICLE · en

Objective: The purpose of this work is to optimize the processing of molecular dynamics (MD) trajectory data obtained for large biomolecular systems. Two popular software tools were chosen as the reference: the tng and the xdrfile libraries. Current implementation of tng algorithms and library is either fast or storage efficient and xdrfile is storage efficient but slow. Our aim was to combine speed and storage efficiency through the xdrfile’s code modification. Results: Here we present libxtc, a ready-to-use library for reading MD trajectory files in xtc format. The effectiveness of libxtc is demonstrated for several biomolecular systems of various sizes (~ 2 × 104 to ~ 2 × 105 atoms). In sequential mode, the performance of libxtc is up to 1.8 times higher and 1.4 times lower than xdrfile and tng, respectively. In parallel mode, libxtc is about 3 and 1.3 times faster than xdrfile and tng. At the same time, MD data stored in the xtc format require about 1.3 times less disk space than those treated with the tng algorithm in the fastest reading mode, which is a noticeable saving especially when the MD trajectory is long and the number of atoms is large—this applies to most biologically relevant systems.

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Dynamic "molecular portraits" of biomembranes drawn by their lateral nanoscale inhomogeneities.

2021 · ARTICLE · en

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 103 nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nano-clusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc. properties at the membrane-water interface attracts increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties.

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Курсы (4)