Biochemistry (Moscow)

An antiviral protein named CCP-27 was purified from the leaves of Celosia cristata at the post-flowering stage by anion-exchange, cation-exchange, and gel-filtration chromatography. It exhibited resistance against sunnhemp rosette virus in its test host Cyamopsis tetragonoloba. It also exhibited deoxyribonuclease activity against supercoiled p BlueScript SK+ plasmid DNA. It was found to nick supercoiled DNA into nicked circular form at lower prote in concentration followed by nicked to linear form conversion at higher protein concentration. CCP-27 also possesses strong ribonuclease activity against Torula yeast rRNA.

P-Glycoprotein (P-gp) is one of the most clinically significant representatives of the ABC transporter superfamily due to its participation in the transport of biotic components and xenobiotics across the plasma membrane. It is known that various chemicals, environmental factors, and pathological processes can affect P-gp activity and expression. In this study, we investigated the role of P-gp in limiting the cell membrane permeability during oxidative stress. Human adenocarcinoma colon cells (Caco-2) overexpressing P-gp were cultured for 72 h in the medium containing hydrogen peroxide (0.1-50 µM). The transport of the P-gp substrate fexofenadine was evaluated in a special Transwell system. The amounts of P-gp and Nrf2 transcription factor were analyzed by the enzyme-linked immunosorbent assay. The concentration of SH-groups in proteins and the contents of lipid peroxidation products and protein carbonyl derivatives were determined spectrophotometrically. Hydrogen peroxide at a concentration of 0.1-5 µM did not significantly affect the studied parameters, while incubation with 10 µM H2O2 decreased in the level of SH groups in cell lysates and increased in the amount of Nrf2 in the cell lysates. Nrf2, in its turn, mediated an increase in the content and activity of the P-gp transporter, thus limiting the increasing permeability of the cell membrane. Hydrogen peroxide at a concentration of 50 µM promoted oxidative stress, which was manifested as a decrease in the content of SH-groups, increase in the concentration of lipid peroxidation products and protein carbonyl derivatives, and decrease in the P-gp level, which led to a significantly increased permeability of the plasma membrane. These results show that the transport and protective roles of P-gp, in particular, reduction of the cell membrane permeability, are affected by the intensity of oxidative stress and can be manifested only if the extent of membrane damage is insignificant.

One of the arguments against aging being programmed is the assumption that variation in the timing of aging-related outcomes is much higher compared to variation in timing of the events programmed by ontogenesis. The main objective of this study was to test the validity of this argument. To this aim, we compared absolute variability (standard deviation) and relative variability (coefficient of variation) for parameters that are known to be determined by the developmental program (age at sexual maturity) with variability of characteristics related to aging (ages at menopause and death). We used information on the ages at sexual maturation (menarche) and menopause from the nationally representative survey of the adult population of the United States (MIDUS) as well as published data for 14 countries. We found that coefficients of variation are in the range of 8–13% for age at menarche, 7–11% for age at menopause, and 16–21% for age at death. Thus, the relative variability for the age at death is only twice higher than for the age at menarche, while the relative variability for the age at menopause is almost the same as for the age at menarche.

The interaction of Yersinia pseudotuberculosis porin solubilized in deoxycholate with the S- and R-forms of endogenous lipopolysaccharide (LPS) was studied by the quenching of intrinsic protein fluorescence. The samples of S-LPS differed both in the length of O-specific polysaccharide (n = 1 and 4) and in the acylation degree of the 3-hydroxytetradecanoic acid residues of the lipid A moiety (12-66%). R-LPS (12%) binding to porin was found to occur with positive cooperativity on two integrated structural regions of the R-LPS macromolecule, namely, core oligosaccharide and lipid A. The mode of porin interaction with low-acylated S-LPSs (15 or 20%) coincided with a model involving three types of binding sites. The shape of Scatchard curves of binding indicates that a complex formation between porin and low-acylated S-LPS is cooperative at low and moderate ligand concentration, whereas at near-saturating LPS concentrations porin binds to LPS independently on two types of binding sites. The O-specific polysaccharide chain in the S-LPS macromolecule increases the affinity of its interaction with porin in comparison with R-LPS–porin binding. A significant increase (to 66%) in the degree of S-LPS acylation substantially changed its porin-binding character: the process becomes anti-cooperative with lowered affinity. Thus, the features of LPS–porin interaction significantly depend on the conformational changes in the LPS molecule due to expanding of its hydrophobic region.

The role of lipid peroxidation product 4-hydroxy-trans-2-nonenal (4-HNE) in functional activity of cells under normal and different pathological conditions is discussed. Different pathways of 4-HNE metabolism in tissues are analyzed, with particular focus on the role the glutathione system in this process. 4-HNE is implicated in regulation of cell growth, proliferation, differentiation, and apoptosis. 4-HNE and metabolic products of other antioxidants (carotenoids) resemble each other in chemical nature of the product and influence general pathways of signal transduction. Manifestation of 4-HNE toxicity under oxidative stress conditions is regarded as a link to many diseases whose pathogenesis is connected with modifications of proteins and nucleic acids.

Somewhere in the region of 3 billion years ago an enzyme emerged which would dramatically change the chemical composition of our planet and set in motion an unprecedented explosion in biological activity. This enzyme used solar energy to power the thermodynamically and chemically demanding reaction of water splitting. In so doing it provided biology with an unlimited supply of hydrogen equivalents needed to convert carbon dioxide into the organic molecules of life. The enzyme, which facilitates this reaction and therefore underpins virtually all life on our planet, is known as Photosystem II (PSII). It is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae, and cyanobacteria. Over the past 10 years, crystal structures of a 700 kDa cyanobacterial dimeric PSII complex have been reported with ever increasing improvement in resolution with the latest being at 1.9 details of its many subunits and cofactors are now well understood. The water splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino acid side chains, of which seven provide ligands to the metals. The metal cluster is organized as a cubane-like structure composed of three Mn ions and the Ca2+ linked by oxo-bonds with the fourth Mn attached to the cubane via one of its bridging oxygens together with another oxo bridge to a Mn ion of the cubane. The overall structure of the catalytic site is providing a framework on which to develop a mechanistic scheme for the water splitting process and gives a blue print and confidence for the development of catalysts for mimicking the reaction in an artificial photo-electrochemical system to generate solar fuels.

Platelets are formed from bone marrow megakaryocytes, circulate in blood for 7-10 days, and then are destroyed in the spleen and/or liver. Platelet production depends on the megakaryocyte population state in the bone marrow: number and size of the cells. The platelet turnover, i.e., the number of platelets passing through the bloodstream in a certain time, is determined by both the rate of their production and the rate of their destruction. The review considers laboratory markers, which are used to assess platelet production and turnover in the patients with hematologic and cardiovascular pathologies. These markers include some characteristics of platelets themselves: (i) content of reticulated (“young”) forms in the blood detected by their staining with RNA dyes; (ii) indicators of the platelet size determined in hematology analyzers (mean volume, percentage of large forms) and in flow cytometers (light scattering level). Alterations of platelet production and turnover lead to the changes in blood plasma concentrations of such molecules as thrombopoietin (TPO, main mediator of megakaryocyte maturation and platelet formation in the bone marrow) and glycocalicin (soluble fragment of the membrane glycoprotein Ib detached from the surface of platelets during their destruction). Specific changes in the markers of platelet production and turnover have been observed in: (i) hypoproductive thrombocytopenias caused by suppression of megakaryocytes in the bone marrow; (ii) immune thrombocytopenias caused by accelerated clearance of the autoantibody-sensitized platelets; and (iii) thrombocytosis (both primary and reactive). The paper presents the data indicating that in patients with cardiovascular diseases an increased platelet turnover and changes in the corresponding markers (platelet size indexes and content of reticulated forms) are associated with the decreased efficacy of antiplatelet drugs and increased risk of thrombotic events, myocardial infarction, and unstable angina (acute coronary syndrome).

Due to the unique capability of modulating cell membrane potential upon photoactivation, channelrhodopsins of green (Chlorophyta) and cryptophytic (Cryptophyta) algae are widely employed in optogenetics, a modern method of light-dependent regulation of biological processes. To enable the search for new genes perspective for optogenetics, we have developed the PCR tests for the presence of genes of the cation and anion channelrhodopsins. Six isolates of green algae Haematococcus and Bracteacoccus from the White Sea region and 2 specimens of Rhodomonas sp. (Cryptophyta) from the regions of White and Black Seas were analyzed. Using our PCR test we have demonstrated the known Haematococcus rhodopsin genes and have discovered novel rhodopsin genes in the genus of Bracteacoccus. Two distantly homologous genes of anion channelrhodopsins were also identified in the cryptophytic Rhodomonas sp. from the White and Black Seas. These results indicate that the developed PCR tests might be useful tool for a broad-range screening of the Chlorophyta and Cryptophyta algae to identify unique channelrhodopsin genes.