Conserved amino acid (aa) sequence motifs (blocks) in the alignment of M.NruI/M.Sbo13I family. Red bold letter indicates invariant aa and h and e indicate secondary structural element α-helix and β-strand respectively. Shaded regions indicate extensions of respective motifs. The number to the left of each sequence indicates the absolute location of the first residue of the segment within the whole sequence. Shaded yellow background indicates hydrophobic aa and shaded blue aa indicates polar or charged residue. Conserved amino acids are grouped as (E, D, Q, N), (V, L, I, M), (F, Y, W), (G, P, A), (K, R) and (S, T), using standard one-letter abbreviations (Malone et al. 1995).