An alpha subtpe methyltransferase that recognizes the double-stranded sequence 5'-GATC-3' and methylates A-2 on both strands (PubMed:12654995) (Probable). May prevent degradation of viral DNA by the host restriction-modification antiviral defense system. a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Monomer. Belongs to the N(4)/N(6)-methyltransferase family.