Conserved amino acid sequence motif (block) organization in different groups of amino DNA methyltransferases. Amino acid motifs in shaded blue (motifs X, I, II, III) contain the AdoMet-binding region, and the motifs in shaded green harbour the catalytic region (motifs IV - VIII). The extra motifs (blocks) Xa and IVa in the M.NruI/M.Sbo13I sub-group are also shown. TRD, DNA target-recognizing domain. N, N-terminus; C, C-terminus.