BREX systems (bacteriophage exclusion) provide immunity against bacteriophage. Part of a type 1 BREX system which protects against dsDNA phage (Probable). This system allows phage adsorption but prevents phage DNA replication, without degradation of the phage DNA. Methylation of bacterial DNA by this protein guides self/non-self discrimination (By similarity). Probably methylates the adenine in the fifth position of the hexamer 5'-ACRCAG-3' in genomic DNA (Probable). N(6)-methylated adenine on the fifth position of 5'-ACRCAG-3' is found in the genome; there are 1906 sites in the genomic DNA (PubMed:25747834). a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Loss of whole genome N(6)-adenine methylation in the fifth position of the hexamer 5'-ACRCAG-3', no visible growth phenotype. Has a higher plasmid acquisition ability (when plasmids have the methylation hexamer) but a reduced ability to retain plasmids. Belongs to the methyltransferase superfamily. PglX adenine methyltransferase family.