[Primary structure and catalytic properties of extracellular ribonuclease from Bacillus circulans]. / Pervichnaia struktura i kataliticheskie svoistva vnekletochnoi ribonukleazy Bacillus circulans.

A comparative research of individual peptide structures obtained after hydrolysing of Bacillus circulans and B. amyloliquefaciens RNases by the Glu-specific staphylococcal protease was carried out by means of mass-spectrometry and Edman degradation methods. A complete amino acid sequence of B. circulans RNase was determined. Gln15, Gly65 and Gln104 residues in B. amyloliquefaciens RNase were found to be substituted by Leu, Ala and Lys residues in B. circulans RNase, respectively. Catalytic properties of the B. circulans RNase in transesterification reactions with poly- and oligonucleotides as substrates were investigated.

[Extracellular alkaline ribonuclease of Bacillus thuringiensis var. subtoxicus]. / Vnekletochnaia shchelochnaia ribonukleaza Bacillus thuringiensis var. subtoxicus.

Intraspecific selection of Bacillus thuringiensis strains producing extracellular alkaline ribonucleases was carried out. Subtoxicus subspecies with increased expression of the enzyme was detected. A method was developed to isolate preparative amounts of homogeneous extracellular RNase of B. thuringiensis var. subtoxicus. The physico-chemical and catalytic properties of the enzyme was studied and compared with extracellular RNases of others Bacillus species. The conclusion about the structural and evolutional conservation of Bacillus extracellular RNases was drawn.

[Extracellular ribonuclease from Bacillus pumilus]. / Vnekletochnaia ribonukleaza iz Bacillus pumilus.

The extracellular ribonuclease (RNAse Bp) was isolated from the cultural medium filtrate of Bacillus pumilus by ammonium sulfate precipitation and two stages of ion-exchange chromatography on carboxymethyl- and phospho-cellulose columns. The amino acid composition and N-terminal amino acid residue have been determined. The kinetic parameters of cleavage reaction of synthetic polynucleotides have been measured. According to their structural homology RNAse Bp has been shown to be similar to RNAses Ba and Bi. Catalytic properties of the enzyme are very close to RNAse Bi.

[Directed synthesis of 2',5'-oligoadenylates with increased stability towards phosphodiesterases]. / Napravlennoe sozdanie 2',5'-oligoadenilatov s povyshennoi ustoichivost'iu k fosfodiésterazam.

Phosphodiesterase stability of synthetic analogs of 2',5'-oligoadenylates, the mediators of antiviral and antiproliferative action of interferons was analysed. The analogs with a 3'-terminal acyclic nucleoside residue were prepared. These analogs were treated with NIH3T3 cell lysate, mice liver homogenate and snake venom phosphodiesterase. All analogs have demonstrated a high stability as compared with the natural 2',5'-oligoadenylate and its 3'-deoxyderivative. The possible biological activity of these stable analogs of 2',5'-oligoadenylates is discussed.

[Topochemical aspects of pyrimidine specificity of ribonuclease A]. / Topokhimicheskie aspekty pirimidinovoi spetsifichnosti ribonukleazy A.

To get insight into the origin of pyrimidine specificity of ribonuclease A, a study of the enzyme interaction with the substrate analogs having a modified nucleobase was undertaken. Pyridine and pyrimidine cyclophosphates were obtained by phosphorylation of 2'(3')-O-dibutyl stannylidene derivatives of nonprotected nucleosides in high yields. The results of kinetic and NMR studies suggested that a substrate should be locked in anti-conformation in the productive enzyme-substrate complex as it was shown for the crystalline complexes of the enzyme with pyrimidine nucleotides by X-ray analysis. The interaction between carbonyl group in position 2 of substrate nucleobase and proton accepting group of the protein (NH of Thr45) was found to be a prerequisite for the specific recognition of a substrate by the enzyme. The rate constants for transformation of lactam form (slow) and lactim form (fast) of pyrimidine substrates were estimated.