A methylase, recognizes the double-stranded sequence 5'-CATG-3', methylates A-2 on both strands and protects the DNA from cleavage by the NlaIII endonuclease. 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. It is uncertain whether Met-1 or Met-57 is the initiator.