Diagram illustrating a putative evolutionary history of the M.Sfi I-M.Mwo I gene pair according to the "permutation-by-duplication" mechanism. Conserved motifs and the TRD are labeled. Protein sequence regions corresponding to the AdoMet-binding subdomain, the catalytic subdomain, the TRD, and non-conserved segments of unknown function are depicted in green, blue, magenta and grey, respectively. Grey labels indicate non-functional regions that are presumably able to fold in solution and do not interfere with the folding of the functional unit. Red vertical bars denote ends generated by new start or stop codons or the boundaries of intragenic deletions. Deleted segments are marked with "Δ". Putative promoters are indicated as pink arrows.