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L A Baratova

Publications and source records attributed to L A Baratova.

At least 19 recordsLinked to original sources
PubMed1992

The organization of potato virus X coat proteins in virus particles studied by tritium planigraphy and model building.

Potato virus X particles containing the intact, undegraded Ps form of the coat protein and particles containing the in situ degraded Pf form of the coat protein, which is devoid of 19-21 amino acids from the N-terminus, were bombarded with thermally activated tritium atoms, and the intramolecular distribution of the tritium label was studied. The tritium planigraphy revealed that the N-terminal region of the coat protein is the most accessible region for both type of PVX particles. The C-terminal region of the coat protein in the intact virus particles is almost inaccessible to the hot tritium atoms, whereas in Pf particles this region becomes available for the tritium label. A model of PVX coat protein tertiary structure was built, taking into account the predicted secondary structure of the protein, the principles of packing alpha-helices and beta-structure in globular proteins, and known biochemical, immunological, and tritium bombardment data. In the model one beta-sheet consisting of beta-strands at regions 1-12, 14-22, and 24-33 flanks the molecule and forms the outside surface of the PVX particles.

Amino Acid Sequence↗
PubMed1992

The topography of the surface of potato virus X: tritium planigraphy and immunological analysis.

Thermally activated tritium atoms were used to probe the surface topography of the coat protein of potato virus X (PVX) potexvirus. The accessibility profile of amino acid residues in the polypeptide chain was determined from data on the intramolecular distribution of tritium label in the PVX coat protein. Tryptic peptides T1 and T2, as well as parts of peptides T3 and T5, from the PVX particles were all located in the N-terminal region of the PVX coat protein and were accessible to tritium labelling, whereas the C-terminal region of the coat protein was practically inaccessible to it. Indirect ELISA and immunoblotting with two PVX-specific monoclonal antibodies confirmed that the N terminus of the coat protein (residues 1 to 56) was exposed on the virus surface, and furthermore that this region forms a highly immunogenic virus-specific antigenic region. The data obtained support the spatial model of PVX, in which the N-terminal amino acids of the coat protein are exposed at the particle surface, and the C-terminal region is buried in the particle. The spatial organization of the PVX coat proteins differs from the model proposed for other filamentous plant viruses such as potyviruses and tobamoviruses where both the N and C termini of the coat protein are located at the particles' surface.

Amino Acid Sequence↗
PubMed1991

A model for the study of the mechanism of a low pH-induced interaction of the virus fusion proteins and cell membranes.

A model is proposed for the study of molecular mechanisms of a low pH-induced interaction of fusion proteins of enveloped viruses and cell membranes. The model consists of large monolamellar liposomes containing ionophore nigericin in their membranes and ectodomains of fusion protein in their inner space. The process of interaction of the protein with the lipid bilayer is triggered by acidification of the liposomal constituents to the pH of fusion with the help of nigericin by adding citric acid to the outer medium. To visualize the protein structural reorganization, the tritium planigraphy was used. Comparison of the values of specific labelling of the proteins and distribution of radioactivity in individual amino acids in control (at neutral pH) and experimental liposome samples (at the pH of fusion) permits to realise the character of protein-membrane interaction. We have obtained the first results in the study of interaction of the bromelain-released soluble ectodomain of the HAXX molecule (BHA)--with the lipid membrane. The observed increase in the protein specific activity and selective increase in the specific activity of hydrophobic amino acids Ile, Phe and Tyr in experimental liposome samples as compared with the controls did not contradict to the conventional concept, that a hydrophobic N-terminus of HA2 subunit of hemagglutinin is responsible for its interaction with lipid membranes.

Hemagglutinin Glycoproteins, Influenza Virus↗
PubMed1990

Prediction of arenavirus fusion peptides on the basis of computer analysis of envelope protein sequences.

Theoretical search and selection criteria for putative fusion peptides of enveloped viruses are proposed. Arenavirus fusion peptides are predicted on the basis of computer-assisted analysis of amino acid sequences of arenavirus envelope proteins and elements of their secondary and tertiary structure. Accordingly, two regions of GP2 surface protein from 5 viruses of Arenaviridae family have been detected with properties typical of fusion peptides of other enveloped viruses. One region, named peptide IV, located at the N-terminus of the GP2 protein, is followed by the other region or peptide V, more likely candidate for the arenavirus fusion peptide.

Amino Acid Sequence↗
PubMed1990

[A comparative study of phenylalanyl-tRNA synthetases from Escherichia coli and Thermus thermophilus by the tritium topography method].

A comparative study of thermostability and amino acid composition of phenylalanyl-tRNA synthetases from E. coli and Thermus thermophilus HB8 has been carried out. In the thermophilic protein the proline, leucine, phenylalanine, arginine content was considerably increased, whereas that of asparagine, isoleucine, serine, threonine and lysine was decreased as compared to the mesophilic protein. Using tritium topography, Pro, (Leu + Ile) and Gly were found to be the most accessible on the surfaces of the both enzymes. In the E. coli enzyme the threonine residues were also easy to access, while on the surface of the thermophilic enzyme arginine residues were more abundant. A quantitative assay of the surface compositions revealed the increased exposure of (Leu + Ile) residues in the thermophilic protein as well as of the charged asparagine and arginine residues. A possible relationship of the observed effects to thermostability is discussed.

Enzyme Stability↗
PubMed1990

Comparative study of the phenylalanyl-tRNA synthetases from Escherichia coli and Thermus thermophlus by the tritium topography method.

A comparative study of thermostability and aminoacid composition of the phenylalanyl-tRNA synthetases from E. coli and Thermus thermophilus HB8 has been carried out. Compared with the mesophilic enzyme, a considerable increase of Pro, Leu, Phe, Arg and decrease of Asx, Ile, Ser, Thr and Lys content have been revealed in the thermophilic protein. Using tritium topography, Pro, (Leu + Ile) and Gly were found to be the most accessible on the surfaces of both the enzymes. In the E. coli enzyme, Thr residues were also easy to access while on the surface of the thermophilic enzyme there were more Arg residues. The quantitative assay of the surface compositions revealed the increased exposure of the (Leu + Ile) residues on the thermophilic protein as well as of the charged Asx and Arg residues. A possible correlation of the observed effects with thermostability is discussed.

Amino Acids↗
PubMed1989

[The amino acids of the blood in patients with peritonitis: the significance of Fisher's index].

Blood plasma amino acid levels in 10 patients with peritonitis are analyzed. Nonsurvivors, in contrast to survivors, had severe amino acid derangements. Aminoacidemia and amino acid imbalance were registered early in the course of the illness. Increased concentrations of aromatic amino acids: phenylalanine and tyrosine, and low concentrations of branched-chain amino acids: valine, leucine, and isoleucine were associated with a decrease of Fisher's index (BCAA/AAA molar ratio) from 3.0 +/- 0.5 (normal) to 2.0 +/- 0.5 which was of high diagnostic and prognostic significance. The nature of such imbalance and its role in protein derangements are discussed.

Adult↗
PubMed1989

[Effect of myocardial ischemia on the metabolism of nonesterified fatty acids].

The pattern of nonesterified fatty acid consumption was assessed on the basis of the arteriovenous difference during the atrial stimulation test in patients with neurocirculatory dystonia and coronary heart disease. NEFA extraction coefficients were shown to be basically different in these two groups of patients, possible evidence of disturbed lipid metabolism in coronary disease.

Adult↗
PubMed1988

The use of thermally activated tritium atoms for structural-biological investigations: the topography of the TMV protein-accessible surface of the virus.

Thermally activated tritium atoms were used for studying the topography of the TMV protein-accessible surface of the virus. The accessibility profile of amino acid residues in a protein polypeptide chain was determined from data on the intramolecular distribution of a tritium label in the TMV protein. It was shown that tryptic peptides T3, T4, T12, the N-terminal region of peptide T1 and the proximal tryptic peptide T8 (located 20 to 25 A (1 A = 0.1 nm) from the viral axis) are accessible to tritium labelling. The fact of tritiation of the viral RNA was detected as well. This evidence was compared with the high-resolution X-ray analysis data for the TMV. A model is suggested to explain the exposure of the buried sites of the virus to thermally activated tritium atoms. The possibilities and limitations of this method in studying the surface topography of proteins in supramolecular systems as well as for location of protein antigenic regions are discussed.

Amino Acid Sequence↗
PubMed1988

[Various properties of cardiac troponin C tryptic peptides].

Using chromatography and preparative polyacrylamide gel electrophoresis, tryptic peptides TP 1 (residues 47-83), TP 2 (residues 84-118) and TP 3 (residues 119-161) were isolated in a highly homogeneous state from cardiac troponin C. Peptides TP 1, TP 2 and TP 3 were found to contain isolated cation-binding sites II, III and IV of cardiac troponin C. The interaction of these peptides with troponins I and T was studied. It was found that only peptide TP 2 could interact with troponin I. Neither of the peptides isolated interacted with troponin T. The cation-binding properties and structural peculiarities of peptide TP 1 were investigated. It was shown that despite its small size (37 amino acid residues), peptide TP 1 retained its ability to bind Ca2+ which caused conformational changes in the peptide structure. This was accompanied by changes in the electrophoretic mobility and absorption of TP 1 on phenyl-Sepharose.

Animals↗
PubMed1986

Ca2+-induced structural change in the Ca2+/Mg2+ domain of troponin C detected by crosslinking.

Rabbit muscle troponin C was selectively modified at Cys-98 by 1,3-difluoro-4,6-dinitrobenzene. The second function of the bifunctional reagent was triggered at alkaline pH in the presence and absence of Ca2+. The crosslinked troponin C was hydrolyzed by trypsin and the peptides containing a dinitrobenzene moiety were isolated. When troponin C was crosslinked in the presence of Ca2+, the single dinitrobenzene-containing peptide was Gly-89-Arg-100, in which Cys-98 was crosslinked with Lys-90. When crosslinking was performed in the absence of Ca2+, beside the above peptide two additional peptides containing dinitrobenzene were found. One of these peptides is made up of two fragments, Ser-91-Arg-100 and Asn-105-Arg-120, crosslinked between Cys-98 and Tyr-109. The second peptide, Ala-121-Lys-140, contains modified Lys-136, presumably crosslinked with His-135. The data indicate that the distances between the alpha-carbon of Cys-98 and those of Lys-90, Tyr-109, Lys-136 and probably the alpha-carbon distance His-125-Lys-136, do not exceed 14 A. Comparison with the X-ray structure of troponin C (Herzberg, O. and James, M.N.G. (1985) Nature 313, 653-659) indicates that some of the above distances increase on Ca2+-binding.

Amino Acids↗
PubMed1985

Specific fragmentation of tRNA and rRNA at a 7-methylguanine residue in the presence of methylated carrier RNA.

The reaction of site-specific cleavage of tRNA at a 7-methylguanine residue, including subsequent treatment with sodium borohydride and aniline [Wintermeyer, W. and Zachau, H.G. (1975) FEBS Lett. 58, 306-309], was shown to work only within a certain range of tRNA concentrations (higher than 30 microM). The Escherichia coli 16S rRNA, which contained a unique m7G (position 527), could not be split by this method when taken at any concentration. It was found that the presence of statistically methylated carrier RNA in the reaction mixture at the borohydride stage significantly stimulates site-specific fragmentation of 16S rRNA and 32P-labeled tRNAs. Direct sequencing proved that 16S rRNA and tRNA are cleaved by this procedure successfully at the m7G residue. The E. coli 16S rRNA was preparatively cleaved by the described procedure into two fragments. The 5'-terminal fragment (1-526) and the 3'-terminal fragment (528-1542) were isolated in the pure form and their secondary structure investigated by the circular dichroism method. The results of this study showed that the secondary and tertiary structures of the 5'-terminal one-third of the 16S rRNA are at least as ordered as those of intact 16S rRNA or its 3'-terminal two-thirds.

Base Sequence↗
PubMed1985

The nucleotide sequence of the gene coding for the 16S rRNA from the archaebacterium Halobacterium halobium.

The complete 1473-bp sequence of the 16S rRNA gene from the archaebacterium Halobacterium halobium has been determined. Alignment with the sequences of the 16S rRNA gene from the archaebacteria Halobacterium volcanii and Halococcus morrhua reveals similar degrees of homology, about 88%. Differences in the primary structures of H. halobium and eubacterial (Escherichia coli) 16S rRNA or eukaryotic (Dictyostelium discoideum) 18S rRNA are much higher, corresponding to 63% and 56% homology, respectively. A comparison of the nucleotide sequence of the H. halobium 16S rRNA with those of its archaebacterial counterparts generally confirms a secondary structure model of the RNA contained in the small subunit of the archaebacterial ribosome.

Archaea↗
PubMed1984

Putative promoter region of rRNA operon from archaebacterium Halobacterium halobium.

The 100 bp sequence from the beginning of the 16S rRNA gene of archaebacterium Halobacterium halobium and the adjacent 800 bp upstream sequence were determined. Four long (80 bp) direct repeats were found in the region preceeding the structural gene of the 16S rRNA. These repeats are proposed to constitute the promoter region of the rRNA operon of H. halobium.

Base Composition↗
PubMed1981

[Serratia marcescens endonuclease. Properties of the enzyme].

Some physico-chemical properties of endonuclease (EC 3.1.4.9) from Serratia marcescens were studied and the amino acid composition of the enzyme was determined. The protein molecule was shown to contain one SH-group and one S-S-bond, which renders it different from the well studied nuclease (EC 3.1.4.7) from Staph. pyogenes. The conditions for reconstitution of the S-S-bond by dithioerythritol for quantitative estimation of cysteine residues of the endonuclease molecule were selected. The N-terminal amino acid was found to be threonine. The UV spectra for the enzyme are typical for proteins; A 0,1% 1cm,280nm is 1.46, epsilon 25 degrees 280nm,pH7,4 is 47292 M-1 cm-1. The sedimentation coefficient in phosphate buffer sW, 20 degrees is 3.4 S, pI is 6.5 and 7.5.

Amino Acids↗
PubMed1979

Intracellular serine proteinase of Bacillus subtilis strain Marburg 168. Comparison with the homologous enzyme from Bacillus subtilis strain A-50.

Intracellular serine proteinase was isolated from sporulating cells of Bacillus subtilis Marburg 168 by gramicidin S-Sepharose 4B affinity chromatography. The enzymological characteristics, the amino acid composition and the 19 residues of the N-terminal sequence of the enzyme are reported. The isolated proteinase was closely related to, but not completely identical with, the intracellular serine proteinase of B. subtilis A-50. The divergence between these two intracellular enzymes was less than that between the corresponding extracellular serine proteinases (subtilisins) of types Carlsberg and BPN', produced by these bacterial strains. This may be connected with the more strict selection constraints imposed in intracellular enzymes during evolution.

Amino Acid Sequence↗