This protein family includes SAM-dependent beta subtype DNA methyltransferases that methylate exocyclic nitrogens and form either N4-methylcytosine (N4-MTases) or N6-methyladenine (N6-MTases) [], including Type III restriction-modification enzyme EcoPI Mod subunit from Escherichia phage P1, a component of the beta subtype methylase that binds the system-specific DNA recognition site 5'-AGACC-3' and methylates A-3 of only 1 strand []. MTRF1L release factor glutamine methyltransferase from humans and Ribosomal RNA small subunit methyltransferase C from the Gammaproteobacteria Hahella chejuensis also belong to this group. They methylate a glutamine residue in the mitochondrial translation release factor MTRF1L []and a guanine in the 16S rRNA respectively.
