[Heterogeneity of DNA-methylases from Escherichia coli CK cells]

The existence of five DNA methylases, differing in their specificity towards the methylated sequence, in the cells of E. coli CK has been demonstrated. Two enzymes methylate cytosine to form 5'-methylcytosine, while three enzymes methylate adenine to form 6'-methylaminopurine. A method consisting in simultaneous isolation of five individual enzymes, which involves gel-filtration of the protein fraction with 0.3-0.6 M ammonium sulfate on Biogel A-05AM, is proposed.