[Recognition sites of adenine DNA-methylases from cells of E. coli]

DNA-methylases from a strain of E. coli CK were studied. Three adenine methylases were found in the strain studied, which were eluted by 0.16 M, 0.23 M and 0.7 M NaCl in phosphocellulose P-11 chromatography. According to this, the enzymes were designated as DM-A16, DM-A23 and MD-A70. Indirect data on the presence of adenine specific methylases dissimilar in their recognition sites in cells of E. coli CK were obtained using the test of additional methylation modified by I. I. Nikol'skaya. These conclusions were confirmed, when the dinucleotide sequence was determined in the recognition site using DM-A23 and DM-A70. The methylase DM-A23 was shown to recognize the dinucleotide sequence 5'...A-T...3' and DM-A70--the sequence 5'...A-G...3'.