A putative methylase that probably protects DNA from cleavage by the MjaORF1200P endonuclease. a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.