Catalytic sites of medicinal leech enzyme destabilase-lysozyme (Mldl). Structure-functional correlation

Based on three-dimensional model of the bifunctional enzyme Destabilase-Lysozyme (mlDL-Ds2) in complex with trimer of N-acetylglucosoamine (NAG)3 the functional role of the stereochemically based group of amino acids (Glu14, Asp26, Ser 29, Ser31, Lys38, His92), in manifestation of glycosidase and isopeptidase activities has been elucidated. By method of site-directed mutagenesis it has been shown that mlDL glycosidase active site includes catalytic Glu14 and Asp26, and isopeptidase site functions as Ser/Lys dyad presented by catalytic residues Lys38 and Ser29. Thus, among the invertebrate lysozymes mlDL presents first example of the bifunctional enzyme with identified position of the isopeptidase active site and localization of the corresponding catalytic residues.     

Stability and transformations of bis-PNA/DNA triplex structural isomers

Structurally isomeric complexes formed between homopyrimidine bis-PNAs (T(2)JT(2)JT(4)-linker-T(4)CT(2)CT(2)) and single- and double-stranded DNA targets were investigated. These complexes are triplexes designated S1, S2 and S3 in order of increased mobility by polyacrylamide gel electrophoresis. It is shown that the S3 isomer is formed only on double-stranded DNA and possesses highest stability. Isomers S2 and S1 are formed upon binding of bis-PNA to double-stranded as well as to single-stranded DNA. It was found that the stability of the isomer S1 increases dramatically in the presence of excess single-stranded oligonucleotide complementary to the bis-PNA. The structure of the stabilized S1 isomer is proposed to consist of two bis-PNA/DNA triplexes. The relationship between the yield of the isomer S1 formed on single-stranded DNA and the bis-PNA concentration was investigated and a kinetic model of the formation of S1 is presented.     

Passive Aseptic Calcification of Fixed Pericardial Biomaterials Is Mediated by Damage to the Structure and Microarchitectonics of Their Extracellular Matrix

Biophysics - Abstract—The mechanism of passive (independent of recipient cells) aseptic calcification of pericardial materials fixed with gluteraldehyde, which are used for the manufacture of...     

Catalytic sites of medicinal leech enzyme destabilase-lysozyme (mlDL): Structure-function relationship

Based on the three-dimensional model of the bifunctional enzyme destabilase-lysozyme of the medicinal leech (mlDL) in complex with trimer of N-acetylglucosamine (NAG)₃ by site-directed mutagenesis method, the functional role of the group of amino acids (Glu14, Asp26, Ser29, Ser31, Lys38, His92) in manifestation of lysozyme (glycosidase, muramidase) and isopeptidase activities has been investigated by site-directed mutagenesis. The results obtained go well with hypothesis, that lysozyme active site of mlDL includes catalytic Glu14 and Asp26 residues, and isopeptidase site functions as Ser/Lys catalytic dyad presented by catalytic residues Ser29 and Lys38. Thus, among the invertebrate lysozymes, mlDL presents the first example of a bifunctional enzyme with identified position of the isopeptidase active site and localization of the corresponding catalytic residues.     

Description and life cycle of <Emphasis Type="Italic">Bathylaimus anatolii</Emphasis> sp.n. (Nematoda,tripyloididae)

Bathylaimus anatolii sp. n. is described and illustrated. The new species resembles B. capacosus Hopper, 1962 but differs from the latter by shorter setae, body and by the c-index and has three onchs in the buccal cavity. The seasonal dynamics of abundance, proportion of adults and larvae, as well as the gravid and nongravid females and males were studied. An elongated breeding season from April to November and a long spring-summer peak of population density with a winter minimum at low temperatures for B. anatolii are characteristic in Peter the Great Bay.     

Cytogenetic effects of low dose radiation with different LET in human peripheral blood lymphocytes and possible mechanisms of their realization

The induction of chromosome damage by the exposure to low doses of gamma-(60)Co and accelerated carbon ions 12C in peripheral blood lymphocytes of different donors was investigated. The complex nonlinear dose-effect dependence at the range from 1 to 50-70 cGy was observed. At the doses of 1-5 cGy the cells show the highest radiosensitivity (hypersensitivity), mainly due to the chromatid-type aberration, which is typical to those spontaneously generated in the cell and believed not to be induced by the irradiation of unstimulated lymphocytes according to the classical theory of aberration formation. With the increasing dose the frequency of the aberrations decreases significantly, in some cases up to the control level. At the doses over 50-70 cGy the dose-effect curve becomes linear. The possible role of the oxidative stress, caused by radiation-induced increase in mitochondrial reactive oxigen species (ROS) release in the phenomenon of hypersensitivity (HS) at low doses is discussed as well as cytoprotective mechanisms causing the increased radioresistance at higher doses.     

Genetic characterization of pathogenic Borrelia, group A14S, isolated in Ukraine

Borrelia Ir-5215, isolated from ticks Ixodes ricinus in Ukraine (the Crimean autonomous region), was identified by the method of the polymorphism of the fragment length of the restriction amplicon of rRNA spacer region 5S-23S. Its Msel-restriction profile was relatively similar to that of B. afzelii. The sequencing of spacer region rrf (5S)-rrl (23S) and 16S rRNA gene, as well as the analysis of the similarity of nucleotide sequences, obtained in the course of these study, revealed the differences between Borrelia sp, lr-5215 and six European species of Borrelia burgdorferi sensu lato and a high level of similarity (more than 95.1% for 5S-23S rRNA and 99.4% for 16S rRNA gene) to three known representatives of genome group A14S (Borrelia spp. A14S, I-77 and PC-Rq17). This suggests that isolated Borrelia lr-5215 is a new representative of pathogenic B. burgdorferi sensu lato genome group A14S, which is spread, together with Central Europe, also in southern Ukraine.     

Heavy Metal Contents in Tissues of Dominant Species of the Benthos and in Bottom Sediments of Zolotoi Rog Bay, Sea of Japan

Data on heavy metal contents in polychaetes and free-living nematodes inhabiting the bottom sediments of Zolotoi Rog Bay near the port of Vladivostok are reported. Chronically high contents of heavy metals (Fe, Cu, Zn, and Cd) were found in the bottom sediments and in the infauna. The levels of some toxic elements in tissues of the polychaete Dorvillea (Schistomeringos) japonica inhabiting polluted sediments of Zolotoi Rog Bay were higher than in worms of this species from relatively clean areas of the Sea of Japan. Similar high concentrations of Fe were found in the polychaete Capitella capitata and the nematode Oncholaimium ramosum. The highest concentrations of Fe, Zn, Cu, and Cd were found in tissues of the free-living nematode O. ramosum. Chronic heavy pollution of the bottom sediments leads to a decrease in the biodiversity of the infauna and to specific metal-tolerant communities.Original Russian Text Copyright © 2005 by Biologiya Morya, Davydkova, Fadeeva, Kovekovdova, Fadeev.