Search PubMed⌕ Search

Biomedical subjects

A A Bayev

Publications and source records attributed to A A Bayev.

At least 55 records · Page 3Linked to original sources
PubMed1979

Primary structure of the nucleic acid from the 1,4-alpha-glucan branching enzyme.

The primary structure of the nucleic acid from the branching enzyme 1,4-alpha-D-glucan: 1,4-alpha-D-glucan 6-alpha-(1,4-alpha-glucano)-transferase (2.5-S RNA) isolated from rabbit muscles has been elucidated. The polyribonucleotide consists of 31 nucleotides; the unique features of the polyribonucleotide are the unusually high content of modified nucleotides (32%) and guanine residues (40%). Apparently 2.5-S RNA belongs to a class of nucleic acids unknown up to now. It is the first time that the structure of a nucleic acid component from a ribonucleoenzyme has been defined. This work is a preprequisite for gaining insight into the intimate activating effect of the poly-ribonucleotide on the enzyme action.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1979

Primary structure of an EcoRI fragment of lambda imm434 DNA containing regions cI-cro of phage 434 and cII-o of phage lambda.

Digestion of phage lambda imm434 DNA with restriction endonuclease EcoRI yields 7 fragments. The shortest among them (1287 bp) contains the right part of the phage 434 immunity region and the phage DNA portion proximal to it. The complete primary structure of this fragment has been determined using the chemical method of DNA sequencing. Hypothetical amino-acid sequences of proteins coded by the cro gene of phage 434 and the cII gene of phage lambda, as well as NH2-terminal amino-acid sequences of the cI protein of phage 434 and the O protein of phage lambda, have been deduced solely on the basis of the DNA sequence. The fragment studied contains also the pR and probably prm promoters and the oR operator of phage 434. The sequence coding for them differs from the respective DNA sequence of phage lambda.

Base Sequence↗
PubMed1979

The mechanism of action of tRNA methylases studied with immobilized tRNAs.

Each of the individual tRNAs immobilized on aminohydroxybutyl-cellulose (ABC) through their oxidized 3'-terminal binds affinitively all methylases present in the enzyme extract irrespective of whether this tRNA will be involved in the following step of methylation or not. These data allow to suggest that (a) the formation of a methylase-tRNA complex and the catalytic act of methylation are indeed autonomous processes and (b) the first step of interaction between tRNAs and tRNA methylases is rather unspecific and consists in the recognition of the whole class of tRNA molecules.

Animals↗
PubMed1977

Complementary addressed modification of yeast tRNA Val 1 with alkylating derivative of d(pC-G)-A. The positions of the alkylated nucleotides and the course of the alkylation in the complex.

Yeast tRNA Val 1 alkylation with 2', 3'-O-4-(N-2-chloroethyl-N-methylamino) benzylidene d(pC-G)-A proceeds at 20 degrees - 30 degrees C in the complementary complexes which are formed by d(pC-G)-A greater than RC1 binding to 3 sequences of tRNA Val 1 : psi-C-G58 in the T loop, C-G40 at the 3'-side of the anticodon loop and C-G18 in the D loop. The reaction in the complexes results in A53, I35, and psi 13 alkylation to form beta-/N-methyl-N-(formylphenyl 17 amino/ethyl-tRNA Val 1 with the relative rate constants of the alkylation that are 3 or 2 orders of magnitude higher than that for the alkylation without a complex formation. It is the third nucleotide from the 5'-terminus of the binding site of the modifying agent that is subjected to alkylation in the t RNA Val 1. The course of the alkylation does not depend on the possible base pairing of the 3'-terminal nucleotide of the reagent. The extent of the reagent binding and the relative rate constants of the alkalytion in the complexes indicate the following order of the complex stability: (psi-C-G58) greater than (CO-G40) approximately (C-G18) at 20 degrees and (psi-C-G58) greater than (C-G40) greater than (C-G18) at 30 degrees.

Alkylating Agents↗
PubMed1977

Primary structure of baker's yeast tRNAVal 2b.

The minor form of valine tRNA from baker's yeast-tRNAVal 2b--purified by column chromatography was completely digested with guanylo-RNase and pancreatic RNase. The products of these digestions were separated by a combination of thin-layer chromatography on cellulose and high voltage electrophoresis on DEAE-paper and then identified. The halves of tRNA Val 2b were prepared by partial digestion with pancreatic RNase, and their complete guanylo-RNase and pancreatic RNase digests were analysed. Basing on the obtained data the primary structure of baker's yeast tRNA Val 2b was reconstructed.

Base Sequence↗
PubMed1976

Studies on chromatin. Free DNA in sheared chromatin.

Chromatin which has been hydrodynamically sheared in a low-ionic-strength buffer lacking divalent cations (I = 0.0005 M) contains a heterogeneous set of deoxyribonucleoprotein particles but no molecules of free DNA. The main finding is that a transference of sheared chromatin to 1--2 mM MgCl2 or to 0.1--0.2 M NaCl results in appearance of completely free DNA molecules. A salt-induced rearrangement of DNA-bound histones but not a partial loss of them is responsible for the observed phenomenon. Formation of free DNA molecules is accompanied by aggregation of the majority of remaining deoxyribonucleoprotein particles. The percentage of free DNA molecules in the chromatin which was sheared to an average DNA length of about 400 base pairs is increased from zero in the initial sample to 8-9% in 1 mM MgCl2 and further to approximately 25% of the total DNA in 0.15 M NaCl, 2 mM MgCl2. Free DNA molecules in the sheared chromatin are observed not only upon isopycnic banding of formaldehyde-fixed deoxyribonucleoproteins in CsCl gradients but also in non-ionic metrizamide gradients with either fixed or unfixed deoxyribonucleoprotein samples. The process of free DNA formation is a reversible one; its direction and the equilibrium state depend in particular on the ionic conditions of the medium.

Animals↗
PubMed1976

On the mechanism of tRNA methylase-tRNA recognition.

In order to further elucidate the mechanism of tRNA methylase-tRNA intreaction the methylation of some individual tRNAs separately and by pairs was performed. In conditions of tRNA excess the methylation rates of positionally analogous nucleotides in tRNA molecules are not summed up when two substrates are simultaneously present in the reaction mixture. The inhibitory action of yeast tRNASer, possessing m5c in position 29, on the methylation of C29 in other individual tRNAs was shown. Yeast tRNAVal which possesses an A residue in position 27 was shown to inhibit the methylation of G27 in E. coli tRNAMet. The data obtained confirm the suggestion that tRNA methylases recognizes the tertiary structure of tRNAs. They show also that the recognition and the proper catalytic action are two autonomous processes and that the former at least in its first stage is rather unspecific.

Animals↗
PubMed1974

Acceptor activity of hypermethylated E. coli tRNAf-Met.

The acceptor activity of normal E. coli tRNA(Met) (f) was compared with that of a preparation with surplus methyl groups introduced by a crude methylase preparation from rat hepatoma. No changes in charging were detected when the aminoacylation was carried out in a homologous system. The data indicate that neither the surplus methyl groups by themselves, nor the eventual changes in spatial arrangement are essential for charging of E. coli tRNA(Met) (f).

Amino Acyl-tRNA Synthetases↗