Characterization of DNA methyltransferase from bovine thymus cells

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Abstract
A DNA methyltransferase was partially purified from bovine thymus heavy cells. The enzyme has MW 130,000, and introduces methyl groups from S-adenosylmethionine into the 5 position of cytosines in DNA. Sequence specificity analysis revealed that about 60% of the total methylation occurred in the 5''d(C-G)3'' doublet. Single-stranded and hemi-methylated DNA were methylated at an elevated rate by the enzyme. The kinetic analysis showed that the reaction obeys a random sequential mechanism. The enzyme apparently serves primarily as a maintenance DNA methyltransferase.