[Restriction endonucleases: the detection of new producer strains and the isolation of enzyme preparations]. / Endonukleazy restriktsii: vyiavlenie novykh shtammov produtsentov i poluchenie fermentnykh preparatov.

The method for analysis of microorganisms for the presence of the modification-restriction systems has been developed. The method has permitted to detect more than 10 new producing strains of restrictases including microorganisms of Rhizobium genus. Some of them are promising for practical use. It has been shown that using selection of clones the strain productivity can be increased. The purification process for the majority of restrictases has been proposed. Some physical and catalytic properties of new enzymes have been studied.

[Detection of aquatic microorganisms from the Black Sea--producers of restriction endonucleases]. / Vyiavlenie vodnykh mikroorganizmov chernogo moria--produtsentov éndonukleaz restriktsii.

300 clones of microorganisms isolated at different stations and from different depths in the Black Sea were screened for restriction endonucleases production. The production of restriction endonucleases was found in 17 clones screened. Three of them were identified to be Alteromonas haloplanktis B1. Restriction endonuclease AhaB1 is an isoshizomer of Sau961. An identified Alteromonas haloplanktis clone B8 produces AhaB8I restriction endonuclease the prototype to which is KpnI. Of the clones isolated three are Moraxella species B4 producing MapB4I restriction endonuclease analogous to BanI, three are Bacillus species producing BspB2I and one is Micrococcus lylae 113 producing Mly1131 analogue of NarI, six Moraxella species B6 produce MspB6I. The isolated producer strains may be used for isolation of above mentioned restriction endonucleases.

[Type II restrictases: a schematic of possible evolutionary connections between enzymes and palindrome tetranucleotide recognition segments]. / Restriktazy II tipa: skhema vozmozhnykh évoliutsionnykh sviazei mezhdu fermentami s palindromnymi tetranukleotidnymi uchastkami uznavaniia.

The data on restriction endonucleases which recognize tetranucleotide palindromic sites are analysed. The rules of restriction endonuclease sites transformation have been formulated, general graph and evolution tree are suggested and discussed.

[Mechanism of reaction catalyzed by RNA-ligase from bacteriophage T4]. / Izuchenie mekhanizma reaktsii, kataliziruemoi RNK-ligazoi bakteriofaga T4.

The dissociation constants of the complexes of RNA-ligase with acceptors, donors and the adenylylated donor A(5')ppAp have been determined on the basis of the inhibition of ATP-pyrophosphate exchange reaction. The dissociation constants of the complexes of the enzyme with "poor" acceptors (oligouridilates) have been shown to be slightly different from those with "good" acceptors (oligoadenylates). The dependence of the reaction velocity of the formation of ligation products on the concentration of acceptors (pA)4, (pU)4 and the adenylylated donor A(5)ppAp has been studied. On the basis of the data obtained the conclusion about the random addition mechanism has been drawn. The reaction takes place in the steady-state conditions in the case of (pA)4 and in the equilibrium conditions--in the case of (pU)4.

[Study of ATP-independent stages of reaction catalyzed by phage T4 RNA-ligase]. / Izuchenie ATP-nezavisimykh stadii reaktsii, kataliziruemoi RNK-ligazoi bakteriofaga T4.

The isotope exchange between [5'-32P]pAP and A(5')ppAp catalyzed by enzyme was shown not to take place in the absence of the acceptor; i. e. the necessity of the acceptor presence during the second step of the process was demonstrated. The isotope exchange reaction between [5'32P]pAp and (pA)5p was studied. It was demonstrated that acceptor (pA)4, slightly whereas the acceptor (pU)4 completely inhibits the isotope reaction. The isotope reaction exchange between [5'-32P]pAp and (pU)4pAp does not take place. The question of existence of adenylated donor elimination mechanism in the presence of "poor" acceptors is considered on the basis of the data obtained.

[Kinetic characteristics of the ATP-pyrophosphate isotope exchange catalyzed by RNA ligase from T4 bacteriophage]. / Kineticheskie kharakteristiki izotopnogo obmena ATP-pirofosfat, kataliziruemogo RNK-ligazoi bakteriofaga T4.

The dependence of initial rate v0 of ATP--PPi exchange reaction catalyzed by RNA-ligase of bacteriophage T4 on the concentration of ATP(s), pyrophosphate (z) and Mgcl2 has been determined. The dependence of v0 on s and z described by the equation v0 = k-1k2E0/(k-1 + K2) (1 + K1/s + k2/z) has been obtained for the reaction of E + S in equilibrium ES in equilibrium E1 + Z, where E--enzyme, E1--adenylylenzyme, S--ATP, Z--pyrophosphate, K1 and K2--constants of equilibrium, k-1, k2--velocity constants of transition of ES to E + S and E1 + Z, E0--complete concentration of enzyme. The low inhibition of the ATP--PPi exchange by the acceptor A(pA)2 and donors pAp, p(Ap)3, pCp has been shown. The dependence of v0 on the concentration of MgCl2 is consent with the incorporation of only dimagnesium salts of substrates in the isotope-exchange reaction.

[Isolation of highly purified RNA ligase from bacteriophage T4]. / Vydelenie vysokoochishchennoi RNK-ligazy bakteriofaga T4.

A technique for isolation of RNA-ligase of bacteriophage T4 was proposed. It is mainly based on the using of Soviet materials and sorbents and includes seven purification stages. The technique enables to isolate about 80 000 units of active enzyme from 100 g of E. coli B cells infected with the phage. T4am N82; that makes up 20% of the activity of the cell extract. The obtained preparations of RNA-ligase are homogeneous by the data of electrophoresis and practically, free of endo- and exonuclease admixtures.