An alpha subtype methylase, recognizes the double-stranded sequence 5'-GATC-3' and methylates A-2. Also acts on 5-hydroxymethylcytosine (hmC)-containing DNA, the normal base in this virus (PubMed:12654995, PubMed:2510127). May prevent degradation of viral DNA by the host restriction-modification antiviral defense system (Probable). a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Optimum pH is 7.0-8.5. Monomer. Belongs to the N(4)/N(6)-methyltransferase family.