Том 73, № 5 (2018)

Neuraminidase A (NanA) from the pathogenic bacteria Streptococcus pneumoniae catalyzes the cleavage of terminal sialic acid residues from oligosaccharide receptors on the surface of human respiratory epithelium cells and is considered to be the key virulence factor. The search for new regulatory ligand-binding sites in the structure of this enzyme is of fundamental interest and can reveal new targets to design drugs for treating pneumonia, meningitis, and other human infectious diseases. The low molecular weight compound optactin has been recently shown to inhibit the activity of the homologous Neuraminidase B (NanB). Furthermore, optactin binds at a separate site of the protein structure, which is topologically different from the catalytic center. The bioinformatic and structural analysis using the pocketZebra method was used to annotate a new, previously unknown site in the NanA structure. This new site is analogous to the optactin binding site in NanB and characterized by the high content of subfamily-specific positions, what indicates the importance of this site for the enzyme function. Molecular modeling was used to study optactin binding at the allosteric sites of the homologous neuraminidases NanA and NanB. Tyr250, Thr251, Lys334, Gln494, Lys499, Lys597, Thr657, and Glu658 residues were shown to stabilize the optactin molecule in the NanB structure, with water molecules playing an important role in the coordination of the ligand. Molecular modeling has shown that optactin binding by NanA is complicated due to substitutions in the subfamily-specific positions of the allosteric center. The peculiarities of the structural organization of the new NanA binding site facilitate the targeted search for complementary ligands that can selectively regulate the activity of this enzyme.

A planar multibiosensor for the simultaneous determination of glucose and lactate is developed by combining the Prussian Blue-based electrocatalyst and the protocol for immobilization of glucose oxidase and lactate oxidase enzymes from solutions with a high content of an organic solvent. High sensitivity coefficients (>80 mA M^–1 cm^–2 for lactate and >20 mA M ^–1 cm^–2 for glucose) are demonstrated by the multibiosensors operating in the flow-injection mode in a thin-layer measuring cell. The linear range of the analyzed concentration is 1–500 μM for lactate and 5–1000 μM for glucose. A multibiosensor can be used repeatedly (the exhibited operational stability is not less than 100 measurements without the need for recalibration), which allows using it for the analysis of diluted blood samples and blood serum. The electrocatalytic system with a multibiosensor demonstrates performance characteristics that are superior to the commercial analyzers.

Multicopper oxidases such as bilirubin oxidase (BOD) from Myrothecium verrucaria and laccase (LC) from the basidial fungus Trametes hirsuta have been used as catalysts in dihydroquercetin (DHQ) oxidative polymerization. The conditions selected enabled good yields of DHQ oligomers, which were then analyzed using UV-vis, FTIR, ¹Н and ¹³С NMR spectroscopy. DHQ oligomers synthesized using both enzymes showed higher thermostability as compared with the monomer. Depending on the oxidase, the products of DHQ polymerization differed in physicochemical properties, and as shown by NMR studies, had different structures.

Drug-sensitive MCF7 cells and drug-resistant MCF7/ADR cells are shown to differ with regard to the vimentin and P-gp expression levels, which is indicative of the coexistence of two drug resistance mechanisms in MCF7/ADR cells. The mesenchymal phenotype of epithelial cells makes a much greater contribution to the resistance mechanisms than the ABC transporter’s overexpression, since the difference in the vimentin expression levels in drug-sensitive and drug-resistant cultures is significantly higher than the difference in the P-gp expression.

Magnetite nanoparticles 2–20 nm in size, forming agglomerates up to 70 nm in size, are obtained by cryochemical synthesis.

Understanding the adaptation mechanisms of proteins from extremophiles has paved the way for the development of new biocatalysts resistant to an extreme proton deficit. In the present work, we study the structural adaptation of NADP-dependent short-chain alcohol dehydrogenase/reductase (SDR) to high temperatures. We present the analysis of the amino acid composition of the SDR sequences, the comparative analysis of the structural elements in the SDR from mesophiles and thermophiles, and the results of the molecular dynamics of the superthermostable short-chain alcohol dehydrogenase from the hyperthermophilic archaeon Thermococcus sibiricus (TsAdh319) and its homologues.