This domain is found at the N-terminus of the methylase subunit of Type I DNA methyltransferases. This domain family is found in bacteria and archaea, and is typically between 123 and 138 amino acids in length. The family is found in association with Pfam:PF02384. Mutations in this region of EcoKI methyltransferase Swiss:P08957 abolish the normally strong preference of this system for methylating hemimethylated substrate [1]. The structure of this domain has been shown to be all alpha-helical.

1: Mutations that confer de novo activity upon a maintenance methyltransferase. Kelleher JE, Daniel AS, Murray NE; J Mol Biol. 1991;221:431-440. PMID:1833555