Kubareva E A, Gromova E S, Romanova E A, Oretskaia T S, Shabarova Z A
Bioorg Khim. 1990 Apr;16(4):501-6.
14-membered DNA-duplexes containing modified nucleoside residues, viz 4-N-methyldeoxycytidine (m4dC), 6-N-methyldeoxyadenosine (m6dA) or deoxyinosine (dI), in only one strand of the recognition site (CCA/TGG) of MvaI and EcoRII endonucleases were synthesized. It was shown that MvaI and EcoRII endonucleases interact with the exocyclic amino groups of the external dC residues and of the central dA residue of the recognition site exposed into the DNA major groove. These endonucleases which are isochizomers were found to possess different mechanisms of substrate cleavage. The ability of MvaI endonuclease to hydrolyze only unmodified strand of methylated duplexes allows one to make site-directed single-strand nicks in double-stranded DNA. Elimination of the 2-NH2-group located in the minor groove of DNA by substituting dI for dG had little, if any, effect on the hydrolytic activity of EcoRII and MvaI endonucleases.
合成了仅在MvaI和EcoRII核酸内切酶识别位点（CCA/TGG）的一条链中含有修饰核苷残基，即4-N-甲基脱氧胞苷（m4dC）、6-N-甲基脱氧腺苷（m6dA）或脱氧肌苷（dI）的14元DNA双链体。结果表明，MvaI和EcoRII核酸内切酶与暴露于DNA大沟中的识别位点外部dC残基和中央dA残基的环外氨基相互作用。发现这些同裂酶核酸内切酶具有不同的底物切割机制。MvaI核酸内切酶仅水解甲基化双链体未修饰链的能力使得能够在双链DNA中进行定点单链切口。用dI替代dG消除位于DNA小沟中的2-NH2基团，对EcoRII和MvaI核酸内切酶的水解活性几乎没有影响。
