A methylase that recognizes the double-stranded sequence 5'-GGTGA-3' and protects the DNA from cleavage by the HphI endonuclease (PubMed:8759008). Probably methylates C-2 on the bottom strand (Probable) (PubMed:12654995). a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Both this methylase and M2.HphI protect DNA from cleavage by HphI. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.