An alpha subtype methylase, recognizes the double-stranded sequence 5'-GATC-3' and methylates A-2 (Probable) (PubMed:12654995). Overexpression leads to hypermutability (PubMed:10383952). May be involved in methyl-directed DNA mismatch repair, initiation of chromosome replication and gene expression (Probable). a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Loss of N6-adenine methylation of 5'-GATC-3' sequences, more sensitive to multiple mutagenic agents. Belongs to the N(4)/N(6)-methyltransferase family.