An alpha subtype methylase, recognizes the double-stranded sequence 5'-GATC-3' and methylates A-2 (PubMed:12654995) (By similarity). May be involved in methyl-directed DNA mismatch repair, initiation of chromosome replication and gene expression (By similarity). a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Belongs to the N(4)/N(6)-methyltransferase family.