Figure 2.

Comparison of the conformations of the "catalytic loop" (motif IV) of N-MTases in stereoview. DNA:m⁶A MTases: M.TaqI (1g38 in PDB) [29] in yellow, M.RsrI (leg2) [55] in red, M.DpnM (2dpm) [56] in green; RNA:m⁶A MTase ErmC' (1qao) [24] in blue; DNA:m⁴C MTase M.PvuII (1boo) [57] in cyan; Mj0882 (1dus) in magenta. The ligand for each protein is shown: AdoMet for M.DpnM and ErmC', S-adenosylhomocysteine for M.PvuII, 5'-methylthioadenosine for M.RsrI, and 5'-[2-(amino)ethylthio]-5'-deoxyadenosine (cofactor analog) and the target deoxyadenosine for M.TaqI. In case of M.RsrI, ErmC' and M.PvuII, whose structures were solved in the absence of the target, the Tyr or Phe sidechain can be easily rotated to the M.TaqI-like orientation to make a face-to-face π-stacking interaction with the target base.