Comparison of TlyA sequences. The sequence of TlyA from M. tuberculosis H37Rv (NCBI accession number: CAB10951) is compared with orthologs from M. smegmatis MC2 155 (NCBI number YP_888048.1), S. coelicolor A3 (NC_003888), G. stearothermophilus (AB126617), T. thermophilus HB8 (AP008226) and S. hyodysenteriae (X61684). The total numbers of residues in the enzymes together with the percentages that are identical and functionally-similar to the M. tuberculosis sequence are listed on the right; these conserved regions are shown as black bars within the sequences. Based on their lengths, the sequences fall into the two distinct groups TlyAI and TlyAII. A consensus from these orthologs is shown highlighting the conserved S4-type RNA binding motif (S4), the S-adenosylmethionine (SAM) binding domain and three motifs indicative of 2′-O-methyltransferases (K, D and K) (Aravind and Koonin, 1999, Feder et al., 2003, Maus et al., 2005b).