Vol 44, No 3 (2018)

Plant defensins form one of the classes of a large family of PR-proteins (pathogenesis-related proteins), which have different structure-functional properties and provide plant survival and adaptation under stress conditions. The defensin synthesis is activated at certain stages of the plant ontogeny, as well as during infection and under the influence of abiotic stress factors. The plant defensins exhibit a broad spectrum of biological activities, including inhibition of a growth of pathogenic microorganisms and parasitic plants, protein biosynthesis, proliferation of tumor cells, proteolytic enzymes, α-amylase, and the HIV-1 reverse transcriptase and blockage of the ion channels. Some of these peptides exhibit allergenic properties. Plant defensins are not only multifunctional peptides which participate in various processes in plants, but also important components of the immune system. This review summarizes data on the structural features of plant defensins and defensin-like proteins, signaling pathways of an activation of their biosynthesis in a plant cell, their biological functions, and their role in the immune response. Possible areas of practical application of these peptides are discussed.

The conditions for peptidome analysis of blood plasma were optimized and the efficacy of the proposed approach was compared with the methods described in the literature. The method implies solution of two main problems: inactivation of blood plasma proteases and dissociation of peptides from major blood plasma proteins, which they are quantitatively associated with. To solve these problems, we proposed a new method of sample preparation. The essence of the method is simultaneous denaturation of plasma proteins plus reduction and alkylation of thiol groups of Cys, which is achieved by heating a blood plasma sample (95°C) in the presence of sodium deoxycholate, tris(2-carboxyethyl)phosphine, and 2-chloroacetamide. After separation of peptides from proteins by ultrafiltration on microcentrifuge filters and removal of sodium deoxycholate, the peptides are identified by LC-MS/MS using a Q Exactive HF (Thermo Scientific) mass spectrometer. As a result of one LC-MS/MS run of the peptide mixture obtained from ~15 μL of blood plasma, 2257 peptide fragments of 867 proteins were identified, which is 1.5 times higher than the values achieved by using the generally accepted method of differential solubilization. Our immediate plans include the use of our approach for cataloguing human blood plasma peptides, as well as establishing the magnitude of individual variability and the features of the peptidome that are related to gender and age.

Circular RNAs (circRNAs) are a new RNA type that show predominantly brain-specific expression pattern in mammals. Their individual representatives, acting as competitive endogenous RNAs, can bind microRNAs and contribute to the protection of functional transcripts. In the model of transient cerebral ischemia in rats, we studied the expression of mGluR₃ and mGluR₅ glutamate metabotropic receptor genes (Grm3 and Grm5). These genes are important participants in the metabolic pathways associated with neurosignaling. In the present study, we found that the rat Grm3 and Grm5 genes, in addition to mRNA, encode circRNAs, which are conserved in humans and rodents. In subcortical brain structures of rats containing a lesion focus, the level of these circRNAs is more stable than that of the corresponding mRNA. Using STarMirDB database analysis, the distribution of the microRNA binding sites along the mRNA molecules of human GRM3 and GRM5 genes which are homologous to the corresponding rat genes was elucidated. It has been revealed that sufficiently large number of binding sites is located within exons, which are also part of conservative circRNAs. The results may indicate the functional role of the circRNAs of the investigated genes as competitive endogenous RNAs in the response of brain cells to ischemia.

2,3-Indolotriterpenic alcohols have been synthesized for the first time by successive modification of 3-oxo triterpenic acids (Fisher reaction, reduction of С17-СOOH, cyanoethylation) and characterized by physicochemical methods of analysis. It has been found that 2,3-indolouvaol and 2,3-indolo-28-cyanoethoxybetulin exhibit antitumor activity in vitro toward NCI-H522 lung cancer (–12.65%) and COLO 205 colon cancer cells (–42.78%), respectively. The activity of 2,3-indolooleanolic and 2,3-indolobetulinic acids toward 19 and 9 cell lines of six and four human cancers, respectively, has been revealed. Indole-fused triterpenoids have been shown to hold promise as objects in the search for novel antitumor agents.

The properties of ion channels formed in membranes by polyene antibiotics of various chemical structure of hydrophilic and hydrophobic chains are investigated. Small differences in a hydrophylic chain with a changed number of hydroxyl and carbonyl groups significantly influence the values of conductivity and selectivity of the polyene channel. The greater number of double bonds in a hydrophobic part of polyene molecules leads to the higher biological activity of antibiotics. Measurement of anion–cationic selectivity of the channels formed by polyenes showed that anionic selectivity, as well as conductivity of channels, decreases among antibiotics: amphotericin B, nystatin, candidin, mycoheptin, and levorin. The study of physical and chemical properties of the single and hybrid ion channels on the bilayer lipid membranes in the presence of polyene antibiotics makes possible to create a theoretically reasonable recommendation for the targeted synthesis of new antibiotics with the desired properties.

The role of C2-substituents in the imidazolone ring of borated GFP chromophore derivatives (4-(2-(difluoroboryl)benzylidene)-1H-imidazol-5(4H)-ones) in the degradation process was studied. It was found that the nature of this substituent hardly affected their photostability, whereas their sensitivity toward nucleophilic reagents decreased with an increase in size and donating properties of the substituent. The results supported an assumption that the introduction of C2 substituents was not a rate-limiting step of the degradation process of these derivatives and complex C2 substituents were not effective tools for the improvement of their stability.

The effect of a protein complex consisting of the homeodomain transcription factor Xanf1 and the HMG-containing transcription factor SoxD (homologue Sox15 in human and mouse, group G of the Sox family) on the formation of a spatial pattern of the Xanf1 gene expression has been studied. The Xanf1 factor determines the early development of the forebrain, and the disturbance of its expression results in the reduction of this part of the brain; the pan-neural factor SoxD is necessary for the formation of the neuroectoderm at the earliest stages of development. The study of the functioning of a complex of these factors is important for understanding the molecular bases of the formation of the nervous system. The functional role of the formation of the SoxD–Xanf1 complex directly in developing embryos of the spur-toed frog Xenopus laevis has been studied using the method of in situ hybridization with probes to Xanf1 mRNA. The analysis of changes in the Xanf1 gene expression by the action of the heterodimeric complex suggests that the inhibitory effect of the repressor Xanf1 on the transcription of its own gene is neutralized in the anterior zone at the neurula stage where it is functionally necessary for the stabilization of the cellular status as the anterior forebrain neuroectoderm.