Sergey A. Siletsky

Scientific group of S. A. Siletsky, PhD. Dr. Sc.

Siletsky S. A. graduated from the Department of Biophysics of the Biological Faculty of Moscow State University. Candidate of Biological Sciences (PhD.) since 1998. In 2012, he defended his doctoral dissertation (Dr. Sc.) on the topic "Molecular mechanism of cytochrome C oxidase membrane potential generation".

r. 428 (А), r. 310 (B)
Теl. 9395549, 9395149

Main research areas:

The main interest of the group is to study the mechanisms of energy conversion at the molecular level in membrane proteins. Special attention is paid to the comparative study of the molecular mechanisms of nanoscale ion pumps using various sources of free energy: terminal respiratory oxidases and light-dependent retinal proteins. Finding out the common features and features of the device of protein ion pumps, establishing common basic structural elements and nodal details is important for the design of biomimetic nanodevices, applied research in photonics, membranology, optogenetics, and medicine.
Terminal heme-copper oxidases catalyze the reduction of oxygen to water in the respiratory chains of mitochondria and bacteria, coupling the chemical reaction with the directed transfer of protons across the membrane. In addition to mitochondrial cytochrome oxidase (and other A-family oxidases), the study of B-family oxidases, which have a unique mechanism that allows them to pump protons with different stoichiometry, use a single proton-conducting pathway (“K-channel”) for substrate and pumped protons, and dispense with carboxyl groups as internal proton donors, has been of great interest in recent years. Of particular interest and the main direction of the group is the use of prestationary kinetic methods (capacitive potentiometry or "direct electrometric Drachev-Kaulen method", flash photolysis, stop flow, etc.) to elucidate the intermediate stages of electron and proton transfer, the spectral characteristics of chromophore groups, the dynamics of the interaction of ligands with the active centers of enzymes.
In the study of retinal proton pumps, the study of the electrogenic mechanism of proton pumping by a number of new retinal proteins is of particular interest. A time-resolved study of charge transfer within retinal proteins during the photocycle provides unique information about the mechanism of molecular membrane pumps. The interest in these objects is caused both by the application of the acquired knowledge in biotechnologies and optogenetics, and by the discovery in recent years of new retinal proteins that differ in their 3-dimensional structure, ion specificity, charge transfer mechanisms, and functions performed. The group is currently actively investigating the retinal protein from the psychotrophic bacterium Exiguobacterium sibiricum (ESR), isolated from permafrost. The unique features of ESR include the absence of carboxyl groups, typical internal proton donors in proton pumps. The recently discovered Heliorhodopsin, which has unique structural and functional properties, is also being investigated.

Main scientific results:

When studying the mechanisms of proton pumping by heme-copper terminal oxidases (since 1994), significant aspects of the organization and arrangement of the molecular mechanism for generating the membrane potential of cytochrome oxidases of the family A, which includes mitochondrial cytochrome oxidase, were established. The results obtained relate to elucidating the push-pull mechanism of coupled proton pumping in each of the 4 separate single-electron stages of the cytochrome oxidase catalytic cycle, determining the role of proton-conducting D and K channels, and determining the stoichiometry and sequence of proton pumping during the catalytic cycle. The results of these studies are summarized in the reviews: (Front. in Biosc., 2013, BBA-Bioenergetics, 2012).
The stages of electron and proton transfer in the catalytic cycle of cytochrome oxidase with 5 redox centers, cytochrome caa3 from T. thermophilus were studied (BBA-Bioenergetics, 2011). The presence of the 5th (additional) redox center allowed us to study the transfer from cytochrome c to the active center of the first electron in the catalytic cycle of cytochrome oxidase, using a natural electron donor (BBA-Bioenergetics, 2013).
The stages of membrane potential generation in the catalytic cycle of the B family cytochrome oxidase from T. Thermophilus are described (BBA-Bioenergetics, 2007), and the features of the coupling mechanism and stoichiometry of proton pumping at a number of stages of the catalytic cycle of this enzyme are revealed (BBA-Bioenergetics, 2009, BBA-Bioenergetics, 2017).
Patterns in the structural and functional organization of proton transport pathways in cytochrome oxidase and photosystem 2 were revealed. These molecular "machines" catalyze the reduction of oxygen to water and the oxidation of water to molecular oxygen, respectively. For the catalytic cycles of both proteins, the relationship between the functional states of the proton transport pathways and the stages of oxygen conversion in the catalytic center is shown (Front. in Biosc., 2017). Switching the proton transport pathways may play a key role in the mechanism of catalysis in both proteins.
In collaboration with the group of V.B. Borisov, PhD. Dr. Sc., aspects of the dynamics of the interaction of CO with the active center of cytochrome bd were clarified and the stages of "reverse" electron transfer were resolved under certain conditions (Plos One, 2014; Plos One, 2016; Biochemistry (Mosc.), 2017); the peculiarities of the sensitivity of bo and bd terminal oxidases from E. coli to carbon monoxide and ammonia are described (BBA-Bioenergetics, 2019; Antioxidants, 2021). The current views on the mechanism of oxygen reduction in two superfamilies of terminal respiratory oxidases: heme-copper oxidases and cytochrome bd, biotechnological and medical applications of bd-oxidases are summarized (Biochemistry (Mosc.), 2019; Antioxid. Redox Signal, 2020).
The electrogenic mechanism of proton pumping by the retinal protein from the psychotrophic bacterium Exiguobacterium sibiricum (ESR) and the role of the lysine K96 residue, unique for retinal proton pumps, in the proton-donor region during proton transfer were investigated (BBA-Bioenergetics, 2016, BBA-Bioenergetics, 2019). The effects on the electrogenic mechanism of the interaction of the primary proton acceptor D85 with the H57 residue, a unique feature of proteorhodopsins, are studied on the example of ESR (BBA-Bioenergetics, 2021).
The stages of proton transfer during the heliorhodopsin photocycle (PNAS, 2020) are resolved, which allows us to conclude about the trajectory of proton movement within the protein and the functional role of proton-carrying groups.
The effects of zinc ions on the P side of the membrane on the electrogenic mechanism of wild-type cytochrome oxidase and mutant forms with substitutions in the proton-conducting D channel are described. The experimental results suggest that there must be two pathways by which the pumped proton can exit the protein from the proton-loading site (PLS) (Biochemistry (Mosc.), 2021).

Participation in joint research projects:

In different years, cooperation with the University of Helsinki (Finland); the University of Illinois at Urbana-Champaign (USA); the University of Osnabruck (Germany), the University of Stockholm (Sweden), the Institute fur Biochemie, Rheinisch-Westfalishe Technische Hochschule, Aachen, (Germany), the University of Limerick (Ireland), the Institute of Biophysics in Szeged (Hungary), the University of California at Irvine (USA), the Institute of Bioorganic Chemistry (IBC RAS) (Russia); the Moscow Institute of Physics and Technology (National Research University) (Russia); the Institute of Structural Biology J.-P. Ebel, the University of Grenoble (France).

Grant support:

Since 2001, the group leader's research has been continously supported by grants from the Russian Foundation for Basic Research: (№ 01-04-49330, 04-04-48556, 06-04-48608, 09-04-00140, 12-04-1000, 15-04-06266, 18-04-00503).

Teaching activities:

Teaching the annual course "Biochemistry" at the Faculty of Bioengineering and Bioinformatics of the Lomonosov Moscow State University. Teaching a semester course “Bioenergetics” (seminars) to students of the Faculty of Bioengineering and Bioinformatics and the Faculty of Biology (undergraduates) of the Lomonosov Moscow State University.

Scientific awards:

The State Prize of the Russian Federation for outstanding work in the field of science and technology for young scientists, the prize of the Biochemical Society of the Russian Academy of Sciences for young scientists of Russia, the prize of the European Academy for Young Scientists of the CIS, the Kaulen Prize for the best work of young scientists of the Belozersky Institute of Physico-Chemical Biology (MSU), grants to support talented students, postgraduates and young scientists of MSU.