PubMed Health⌕ Search

Biomedical subjects

R I Tatarskaia

Publications and source records attributed to R I Tatarskaia.

16 recordsLinked to original sources
PubMed1978

[Inhibitors of exonuclease A5].

Over 30 compounds resembling to or being structural elements of the minimal substrate of exonuclease A5 were tested for their ability to inhibit the reaction catalyzed by this nuclease. The compounds containing less than two phosphate groups were shown to possess a low inhibitory activity, if any. CDP, double-stranded DNA and nucleoside-3',5'-diphosphates (pNp) proved to be effective exonuclease A5 inhibitors. Pyrophosphate stimulated the reaction in the case of low molecular weight substrates only. For the inhibitory activity of pNp to occur, the intactness of the nucleoside moiety as a whole was shown to be necessary, the activity level depending on the structure of both the base and the sugar components. A competitive mechanism of the inhibitory action was demonstrated for pTp, pdCp, pdGp, pdAp and pUp and the Ki values were determined. The affinity for the inhibitor decreased in the following order: pdCp greater than or equal to pTp greater than pdGp greater than pdAp. Ki for pdCp and pTp were found to be approximately 3.10(-6) M. The investigation of the inhibition mechanism as well the determination of Ki were accomplished with the help of homogenous low molecular weight substrates--ApApA and the phosphoamide MeOPheNH(pdA)2. These were chosen after kinetic parameters determination of the hydrolysis of 22 exonuclease A5 substrates, predominatly of the RpNpN type. On the basis of data obtained the specificity of exonuclease A5 is also discussed. Possible usefulness of immobilized competitive inhibitors of the pNp type not only for single nuclease isolation but for the separation of a mixture of different nucleases is considered. This possibility is based on the almost universal inhibitory effect of pNp on different nucleases and at the same time on their different affinity for the enzymes. In particular, this approach might be useful for the elimination of exonucleases and some other nucleolytic enzymes from the preparations of endonucleases-restrictases.

Cytidine Diphosphate↗
PubMed1976

[A mechanism of mononucleotide formation under endonuclease hydrolysis].

It has been shown under poly-A hydrolysis by endonuclease A236 in the presence of large amounts of E. coli phosphatase that the formation of mononucleotides requires the presence of terminal 5'-P in the substrate. Simultaneously, it has been found for endonuclease A236 and nuclease of Serratia marcescens that the products of exhaustive hydrolysis carried out in the presence of excess amounts of phosphatase contain an additional nucleoside residue as compared to the ordinary products of exhaustive hydrolysis, the number of phosphate groups being equal in both cases.

Endonucleases↗
PubMed1976

[Some peculiarities of transfer RNAs hydrolysis by exonuclease A5].

Unusual kinetics of the hydrolysis of the baker's yeast total tRNA and tRNA1Val by exonuclease A5 was found (two stages of the reaction; low initial velocity and still lower velocity of the second reaction stage; high Km values). These peculiarities were shown to be due to the three-dimensional structure of the substrate, which makes a large part of the tRNA molecule resistant to the exonuclease A5 attack. The exhaustive tRNA hydrolysis observed in the presence of very large doses of exonuclease A5 may be explained by a slight (less than 1%) endo-RNAase contamination in the exonuclease A5 preparation. The hydrolysis conditions become optimal, i.e. the exhaustive hydrolysis proceeds most rapidly, when the amount of endo-RNAase admixture reaches 20--30%. The artificial enzyme mixture of such a composition is a convenient reagent for RNA and expecially for tRNA hydrolysis under mild conditions to 5'-mononucleotides. The considerable resistance of tRNA to pure exonuclease A5 action will make it possible porbably to use tRNA instead of circular nucleic acids for endonuclease admixtures estimation in enzyme preparations.

Exonucleases↗
PubMedDate not supplied

[Isolation of exonuclease A5 preparation free of phosphomonoesterase contamination].

A method is described of the isolation of exonuclease from cultural medium of Actinomyces sp. of coelicolor type, strain 5. The enzyme preparation is practically free from phosphatase activity (the ratio between exonuclease and phosphatase activities is about 10000). Chromatography on DEAE-Sephadex after the heating of the enzyme preparation at 37 degrees C and pH 5.5 in the presence of 2-mercaptoethanol was used to elimate the phosphatase contamination. The preparation of exonuclease A5 is suitable for different structural studies of nucleic acids, it can be used (instead of snake venom PDE) in a large scale preparation of 5'-mononucleotides from nucleic acids as well.

Actinomyces↗
PubMedDate not supplied

[Nucleases. Biological role].

In the first part of the review (R. I. Tatarskaya, 1976, Mol. Biol. 10, 235--259) the role of nucleases in the transcription, DNA replication, recombination and reparation was briefly described and discussed. The second part comprises some data on the role of nucleases in tRNA, rRNA, mRNA and DNA processing and mRNA degradation. Brief chapters "Restriction" and "Nucleases and viruses" are included as well.

Base Sequence↗