A methylase, recognizes the double-stranded sequence 5'-GATATC-3', methylates A-? on both strands, and protects the DNA from cleavage by the CeqI endonuclease. a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine