Publications by authors named "Iu B Alakhov"

Thermophilic and thermoresistant strains of bacilli were screened on a medium containing Chrome Azurol S for producers of siderophores. It was found that the Bacillus licheniformis VK21 strain dramatically increases secretion of the metabolite, a chelator of Fe3+, in response to addition of manganese(II) salts. The growth of the producer on a minimum medium containing MnSO4 under the conditions of iron deficiency is accompanied by the accumulation of a catechol product, the content of which reaches a maximum at the beginning of the stationary growth phase of culture.

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Fourteen thermophilic and thermostable strains of the genus Bacillus were studied. Total DNA was isolated from these strains and used as a template to identify and clone peptide synthetase genes by means of polymerase chain reaction. Amplified DNA fragments were cloned into a phasmid vector, and nucleotide sequences of cloned fragments were determined.

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Three 18-membered analogues of the N-terminal fragment of the sarcotoxin IA cationic antimicrobial peptide were synthesized by the solid phase method of peptide synthesis with the use of swellographic monitoring. The ability of these peptides to inhibit the growth of various bacteria in culture medium and their hemolytic activity in experiments on human erythrocytes were studied. The analogue completely corresponding to the N-terminal amino acid sequence of the natural sarcotoxin IA with the amide group on its C-terminus exhibited higher antibacterial activity.

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A collection of thermophilic strains of the genus Bacillus was made. The strains were screened for antimicrobial activity. Strains VK2 and VK21 isolated from thermal springs of the Kamchatka Peninsula, and antagonistic to several gram-positive bacterial species were chosen for further investigation of antibiotics produced by them.

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Recombinant plasmids containing genes for the green fluorescent protein (GFP) from Aequorea victoria and the photoprotein obelin from Obelia longissima linked in-frame by inserts differing in nucleotide sequences were constructed. The expression of the chimeric genes in Escherichia coli cells resulted in synthesis of the GFP-obelin hybrid proteins. These proteins were purified to homogeneity and subjected to limited trypsinolysis.

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Here we describe a method for obtaining a ready-to-use stabilized reaction mixture for in vitro translation of mRNA. We also demonstrate the stabilization of a complete translation mixture containing wheat germ extract, amino acids, ATP, GTP, creatine phosphate, creatine kinase, and the reaction buffer by lyophilization in the presence of various sugars. The greatest stabilizing effect is achieved by supplementing the mixture with 10% (mass/volume) trehalose, which is also a unique translation activator, enhancing the translation of various mRNAs.

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The N-terminal 60-kDa-fragment of elongation factor 2 from rat liver (EF-2) was obtained by the limited proteolysis of native EF-2 with elastase. This fragment consists of 506 N-terminal amino acid residues of EF-2. The conformational properties of both this fragment and EF-2 in solution were studied by circular dichroism and fluorescent spectroscopy.

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N-Terminal fragments of the rat liver elongation factor EF-2 containing 162 (17 kDa) and 244 (27 kDa) amino acid residues of 857 (95 kDa) residues of the native protein were synthesized in E. coli cells and in a wheat germ cell-free translation system, and their conformations were studied. Both fragments were synthesized as inclusion bodies (nonspecific molecular aggregates).

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Limited hydrolysis of EF-2 with trypsin in mild conditions leads to cleavage at the N-terminal part of the protein, at the region of phosphorylation, at the Arg54 and Arg65 residues. The trypsinolysis product, fragment T1', containing Thr56 and Thr58, which are phosphorylated in EF-2, is also phosphorylated by EF-2-kinase at the same residues. In the phosphorylated EF-2, digestion by trypsin takes place only at Arg65, resulting in a reduction of the rate of hydrolysis in comparison with the native EF-2.

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A number of cDNA clones coding for 417 amino acid residues of the central part of the rat liver elongation factor 2 (EF-2) have been isolated. The oligonucleotides complementary to EF-2 mRNA were used as primers for synthesis of the first strand of cDNA cloned. Structures of these oligonucleotides were determined in course of 3'----5' sequencing coding strand of EF-2 cDNA.

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The amino acid sequence of cysteine- and cystine-containing peptides resulting from cleavage of the G-factor by cyanogen bromide has been determined. For structure analysis cyanogen bromide peptides were further degradated using trypsin, chymotrypsin, thermolysin, staphylococcal glutamic protease, or limited acid hydrolysis. The products of the G-factor cleavage at Asp-Pro bonds were also studied.

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Products of tryptic hydrolysis of the maleic anhydride modified fragment Th3 from limited thermolytic hydrolysis of the G-factor have been studied. Some short peptides which result from the trypsin action on the native G-factor molecule and belong to the fragment T4 obtained on limited trypsinolysis of the G-factor have been separated and their structure has been studied. As a result amino acid sequence has been determined by tryptic peptides containing 322 amino acid residues of the fragment T4 which makes up about 94% of its polypeptide chain.

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For fragment T4, obtained on limited trypsinolysis of the G-factor, the amino acid sequence embracing 76% of its structure has been determined by analysis of peptides resulting from the fragment T4 cleavage with staphylococcal glutamic protease. These data permitted to assemble into one polypeptide chain 7 out of 12 earlier characterized cyanogen bromide peptides contained in the fragment T4.

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Peptides obtained as a result of cyanogen bromide cleavage of the G-factor have been studied. All 12 peptides embracing the whole structure of fragment T4 have been isolated. For their amino acid sequence determination, cyanogen bromide peptides have been further cleaved with trypsin, chymotrypsin, thermolysin, staphylococcal glutamic protease and BNPS-skatole.

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The amino acid sequence of the C-terminal domain of the elongation factor G (EF-G) has been studied. The polypeptide chain of the domain consists of 228 amino acid residues, and contains no tryptophan or cysteine residues. To determine its structure, the peptides obtained as a result of the fragment digestion by staphylococcal glutamic protease, cyanogen bromide cleavage, and tryptic hydrolysis of the fragment modified by maleic anhydride have been analyzed, as well as peptides obtained after hydrolyses of cyanogen bromide fragments with chymotrypsin, thermolysin and trypsin.

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Using chemical modification and spectrofluorimetry, it was shown that two tryptophane residues of the elongation factor G (EF-G) in positions 51 and 71 from the N-terminus are located on the surface of the EF-G molecule. The tryptophane residue in position 71 is effectively shielded against modification at binding of EF-G guanyl nucleotides. Modification of these tryptophane residues does not result in a loss of the nucleotide-binding activity but completely inhibits EF-G binding to the ribosome.

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