A methyltransferase that methylates the C-1 in the sequence 5'-GGCC-3' and both cytosines in the sequence 5'-CCGG-3' (Probable). A methyltransferase that methylates C-3 within the sequence 5'-GGCC-3', C-1 in 5'-CCGG-3' and C-2 in 5'-CCWGG-3'. Modification confers resistance against restriction enzymes that recognize these sequences (PubMed:12654995). a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Monomer. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.