Structural Studies of Component of Lysoamidase Bacteriolytic Complex from <Emphasis Type="Italic">Lysobacter</Emphasis> sp. XL1

The lysoamidase bacteriolytic complex (LBC) comprising five enzymes (L1–L5) is secreted into the culture liquid by gram-negative bacterium Lysobacter sp. XL1. The medicinal agent lysoamidase has a broad-antimicrobial spectrum. Bacteriolytic protease L1 belongs to the LBC. Recombinant L1 protease of Lysobacter sp. XL1 was expressed, purified to homogeneity and crystallized. The X-ray structure of L1 at 1.35 Å resolution has been determined using the synchrotron data and the molecular replacement method. L1 protease is a thermostable whose thermal unfolding proceeds in one step without forming stable intermediates. Structural information concerning L1 will contribute to the development of new-generation antimicrobial drugs, whose application will not be accompanied by the selection of resistant microorganisms.     

Intraspecific nuclear DNA variation in Drosophila

We have summarized and analyzed all available nuclear DNA sequence polymorphism studies for three species of Drosophila, D. melanogaster (24 loci), D. simulans (12 loci), and D. pseudoobscura (5 loci). Our major findings are: (1) The average nucleotide heterozygosity ranges from about 0.4% to 2% depending upon species and function of the region, i.e., coding or noncoding. (2) Compared to D. simulans and D. pseudoobscura (which are about equally variable), D. melanogaster displays a low degree of DNA polymorphism. (3) Noncoding introns and 3' and 5' flanking DNA shows less polymorphism than silent sites within coding DNA. (4) X-linked genes are less variable than autosomal genes. (5) Transition (Ts) and transversion (Tv) polymorphisms are about equally frequent in non-coding DNA and at fourfold degenerate sites in coding DNA while Ts polymorphisms outnumber Tv polymorphisms by about 2:1 in total coding DNA. The increased Ts polymorphism in coding regions is likely due to the structure of the genetic code: silent changes are more often Ts's than are replacement substitutions. (6) The proportion of replacement polymorphisms is significantly higher in D. melanogaster than in D. simulans. (7) The level of variation in coding DNA and the adjacent noncoding DNA is significantly correlated indicating regional effects, most notably recombination. (8) Surprisingly, the level of polymorphism at silent coding sites in D. melanogaster is positively correlated with degree of codon usage bias. (9) Three proposed tests of the neutral theory of DNA polymorphisms have been performed on the data: Tajima's test, the HKA test, and the McDonald-Kreitman test. About half of the loci fail to conform to the expectations of neutral theory by one of the tests. We conclude that many variables are affecting levels of DNA polymorphism in Drosophila, from properties of nucleotides to population history and, perhaps, mating structure. No simple, all encompassing explanation satisfactorily accounts for the data.      

A molecular phylogeny for the Drosophila melanogaster subgroup and the problem of polymorphism data

Drosophila melanogaster belongs to a closely related group of eight species collectively known as the melanogaster subgroup; all are native to sub-Saharan Africa and islands off the east coast of Africa. The phylogenetic relationships of most species in this subgroup have been well documented; however, the three most closely related species, D. simulans, D. sechellia, and D. mauritiana, have remained problematic from a phylogenetic standpoint as no data set has unambiguously resolved them. We present new DNA sequence data on the nullo and Serendipity-alpha genes and combine them with all available nuclear DNA sequence data; the total data encompass 12 genes and the ITS of rDNA. A methodological problem arose because nine of the genes had information on intraspecific polymorphisms in at least one species. We explored the effect of inclusion/exclusion of polymorphic sites and found that it had very little effect on phylogenetic inferences, due largely to the fact that 82% of polymorphisms are autapomorphies (unique to one species). We have also reanalyzed our previous DNA-DNA hybridization data with a bootstrap procedure. The combined sequence data set and the DNA-DNA hybridization data strongly support the sister status of the two island species, D. sechellia and D. mauritiana. This at least partially resolves what had been a paradox of parallel evolution in these two species.      

Immunological and functional characteristics of the blast cells in acute monoblastic and acute myeloblastic leukemias

The increase in the expression of membrane receptors of monoblast cells to the Fc-fragment of immunoglobulins of classes IgG, IgA, IgM, to the C3-component of complement and FcH receptor in 8 patients with acute monoblastic leukemia and in 3 patients with acute myelomonoblastic leukemia, compared to results obtained for 11 patients with acute myeloblastic leukemia. Leukemic cells in the cases of acute myelomonoblastic and monoblastic leukemia maintained such properties of the phagocytosis (restoring Nitro-blue tetrazolium). Distinctions in degrees of expression of membrane receptors and functional activity of monoblastic and myeloblastic cells may be used as criteria of differential diagnosis of acute monoblastic and acute myeloblastic leukemia.     

The state of dog's metabolism after long interval after oxide tritium administration

An attempt to evaluate the influence of tritium oxide on the metabolism by some indices of lipid metabolism (common lipids, beta-lipoproteins, cholesterin), protein metabolism (cholinesterasa) and carbohydrate metabolism (blood sugar) was made. It was established that the introduction into organism of tritium oxide in the quantities, which could form lethal and sublethal doses of internal radiation, provoked the main changes of values of mentioned indices of metabolism. The character of metabolism changes in the remote period allows us to judge about the development of sclerosis processes, which can be the result of radiation-stipulated acceleration of organism aging.     

Parameters of reactive oxygen species and nitric oxide metabolism in people with high arterial blood pressure

An exchange of active forms of oxygen and nitric oxide in normal conditions and under the development of oxidative stress in humans with high of arterial blood pressure was studied. The activity of NO-synthase was estimated in the human thrombocytes. The nitric oxide formations were determined by the quantity level of its final metabolites--nitrites and nitrates. The peroxynitrite formations were determined by the quantity level of 3-nitrotyrosine. An analysis of the investigation results has shown the increase of processes of oxidative stress, violation of nitric oxide formation in humans with high arterial blood pressure. Application of ascorbic acid allows to reduce the level of free radicals and to increase the formation of nitric oxide, but does not result in statistically reliable changes of the parameters describing formation of peroxynitrite and products of peroxide oxidation of lipids in humans with high arterial blood pressure. Application of ascorbic acid does not result in changes of researched parameters in the control group.     

Detailed analysis of RNA-protein interactions within the ribosomal protein S8-rRNA complex from the archaeon Methanococcus jannaschii

The crystal structure of ribosomal protein S8 bound to its target 16 S rRNA from a hyperthermophilic archaeon Methanococcus jannaschii has been determined at 2.6 A resolution. The protein interacts with the minor groove of helix H21 at two sites located one helical turn apart, with S8 forming a bridge over the RNA major groove. The specificity of binding is essentially provided by the C-terminal domain of S8 and the highly conserved nucleotide core, characterized by two dinucleotide platforms, facing each other. The first platform (A595-A596), which is the less phylogenetically and structurally constrained, does not directly contact the protein but has an important shaping role in inducing cross-strand stacking interactions. The second platform (U641-A642) is specifically recognized by the protein. The universally conserved A642 plays a pivotal role by ensuring the cohesion of the complex organization of the core through an array of hydrogen bonds, including the G597-C643-U641 base triple. In addition, A642 provides the unique base-specific interaction with the conserved Ser105, while the Thr106 - Thr107 peptide link is stacked on its purine ring. Noteworthy, the specific recognition of this tripeptide (Thr-Ser-Thr/Ser) is parallel to the recognition of an RNA tetraloop by a dinucleotide platform in the P4-P6 ribozyme domain of group I intron. This suggests a general dual role of dinucleotide platforms in recognition of RNA or peptide motifs. One prominent feature is that conserved side-chain amino acids, as well as conserved bases, are essentially involved in maintaining tertiary folds. The specificity of binding is mainly driven by shape complementarity, which is increased by the hydrophobic part of side-chains. The remarkable similarity of this complex with its homologue in the T. thermophilus 30 S subunit indicates a conserved interaction mode between Archaea and Bacteria.