Vol 89, No 12 (2024)

Skeletal muscles account for ~30-40% of the total weight of human body and are responsible for its most important functions, including movement, respiration, thermogenesis, and glucose and protein metabolism. Skeletal muscle damage negatively impacts the whole-body functioning, leading to deterioration of the quality of life and, in severe cases, death. Therefore, timely diagnosis and therapy for skeletal muscle dysfunction are important goals of modern medicine. In this review, we focused on the skeletal troponins that are proteins in the thin filaments of muscle fibers. Skeletal troponins play a key role in regulation of muscle contraction. Biochemical properties of these proteins and their use as biomarkers of skeletal muscle damage are described in this review. One of the most convenient and sensitive methods of protein biomarker measurement in biological liquids is immunochemical analysis; hence, we examined the factors that influence immunochemical detection of skeletal troponins and should be considered when developing diagnostic test systems. Also, we reviewed the available data on the skeletal troponin mutations that are considered to be associated with pathologies leading to the development of diseases and discussed utilization of troponins as drug targets for treatment of the skeletal muscle disorders.

The current work provides a comparative assessment of the designed DNA aptamers affinity for the extracellular domain of the human epidermal growth factor receptor (EGFR*). The affinity data of the 20 previously published aptamers are summarized. The diversity of aptamer selection methods and techniques requires the unification of comparison algorithms, which is also necessary for designing aptamers used in post-selection fitting to the target protein EGFR*. In this study the affinity of DNA aptamers from two families – U31 and U2, previously obtained by Wu et al. from the same selection [Wu et al. (2014) PLoS One, 9, e90752] and their derivatives – GR20, U2s and Gol1, obtained by us through rational development, was compared. The aptamer affinity for EGFR* was measured by two different methods: a solution-phase technique – fluorescence polarization of FAM-labeled aptamers, and by a kinetic method using biolayer interferometry technique with aptamers immobilized on the surface. Unlike the values of equilibrium dissociation constants obtained through titration and expressed in units of protein concentration, the analysis of the titration profiles themselves and the kinetics of interaction proved to be more informative. This allowed us to identify how even subtle changes in the aptamers and their structures affect the affinity. Hypotheses regarding the “structure–function” relationships and recognition mechanisms were formulated. The data obtained for the set of aptamer constructions are critical for moving forward to examination of aptamer interactions with EGFR on the cell surface.

Rathayibacter festucae VKM Ac-1390T (family Microbacteriaceae, class Actinomycetes) contains three glycopolymers in the cell wall. The structures of glycopolymers established by chemical and NMR spectroscopy methods. One of them, rhamnomannan, built from repeating tetrasaccharide units carrying side xylopyranose residues, →2)-α-[β-D-Xylp-(1→3)]-D-Rhap-(1→3)-α-D-Manp-(1→2)-α-D-Rhap-(1→3)-α-D-Manp-(1→. The second polymer, found in minor amounts in the strain studied, is rhamnan, →2)-α-D-Rhap-(1→3)-α-D-Rhap-(1→. The third polymer is teichuronic acid, acetalated with pyruvic acid, →2)-α-[4,6-S-Pyr]-D-Manp-(1→4)-α-L-Rhap-(1→4)-β-D-Glcp-(1→4)-α-D-Glcp-(1→4)-β-D-GlcpA-(1→. The structures of rhamnomannan and teichuronic acid are new for Ratayibacter and prokaryotes in a whole. The results of the present study expand our understanding of the structural diversity of microbial glycopolymers and are consistent with the data on the specificity of the structures and composition of glycopolymers for species of the genus Rathayibacter described previously.

The nuclear export protein (NEP) of the influenza A virus, being one of the key components of the virus life cycle, is a promising model for studying the characteristics of formation of amyloids by viral proteins. Using atomic force microscopy, comparative studies of the aggregation properties of recombinant NEP variants, including the protein of natural structure, as well as modified variants with N- and C-terminal affinity His₆-tags, were carried out. All protein variants under physiological conditions are capable of forming aggregates of various morphologies: micelle-like nanoparticles, flexible protofibrils, rigid amyloid fibrils, etc. The His₆-tag attached to the C-terminus has the greatest effect on the aggregation kinetics and morphology of nanoparticles, which indicates the important role of the C-terminal domain in the process of protein self-assembly. Molecular dynamics simulation hasn’t revealed the substantial influence of His₆-containing fragments on the protein structure but demonstrated some variations in the mobility of these fragments that may explain the observed differences in the aggregation kinetics of different NEP variants. Hypothetical mechanisms for the formation and interconversion of various aggregates are considered.

Bacterial and viral RNA polymerases are promising targets for the development of new transcription inhibitors. One of the potential blockers of RNA synthesis is 7,8-dihydro-8-oxo-1,N6-ethenoadenine (oxo-εA), a synthetic compound that is a combination of two modifications of adenine: 8-oxoadenine and 1,N6-ethenoadenine. In this study we synthesized oxo-εA triphosphate (oxo-εATP) and showed that it could be incorporated by RNA-dependent RNA polymerase of the SARS-CoV-2 virus into the synthesized RNA opposite template residues A and G in the presence of Mn2+ ions. In the case of Escherichia coli RNA polymerase, the incorporation occurred opposite A residues in the template DNA strand. If oxo-εA was present instead of adenine in the template DNA strand, transcription was completely stopped at the site of modification. At the same time, oxo-εATP did not suppress RNA synthesis by both RNA polymerases in the presence of unmodified nucleotides. Thus, oxo-εA modification significantly disrupts the template properties of the nucleotide during RNA synthesis by RNA polymerases of different classes, and the corresponding nucleotide derivatives are not potential antiviral or antibacterial transcription inhibitors.