Component of antiviral defense system DISARM (defense island system associated with restriction-modification), composed of DrmE, DrmA, DrmB, DrmC and DrmMII. DISARM is probably a multi-gene restriction module, this subunit is a DNA methylase. Expression of DISARM in B.subtilis (strain BEST7003) confers resistance to phages Nf, phi29, phi105, phi3T, SPO1, SPR and SPP1. Protection is over 10(7)-fold against phi3T, 10(4)-10(5)-fold against Nf, phi29, phi105 and SPR, 100-fold against SPO1 and 10-fold against SPP1. DISARM does not interfere with phage adsorption, but instead interferes with (phi3T) DNA replication early in its cycle, preventing replication, circularization and lysogeny and probably causes phage DNA degradation (DNA is degraded in SPP1-infected cells). Expression of this methylase alone leads to highly methylated phage, however they are still susceptible to the DISARM system. A methylase, recognizes the double-stranded sequence 5'-CCWGG-3', methylates C-2 on both strands. Phage Nf does not have any 5'-CCWGG-3' motifs but is still targeted by the DISARM system. a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Cannot be deleted in a DISARM-containing strain of B.subtilis. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.