Alignment of Catharanthus roseus S-methyltransferase 1 (CrSMT1) with the crystallized caffeic acid O-methyltransferase (COMT) from Medicago sativa. Marked positions; residues and numbering from the M. sativa COMT (Zubieta et al., 2002): a, catalysis (transmethylation): W266, H269, D270, E297 and E330; b, SAM binding: D206–G212, D231, L232, D251–F253, K265 and W271; c, methyl acceptor binding: A162, A322, H323 and N324; d, binding of propanoid tail (e.g. of caffeic acid) in COMT: M130, M180, I316 and M320.