RsmC catalyzes the transfer of a methyl group from S-adenosyl-l-methionine (SAM) to G1207 in hairpin 34 of 16S rRNA (m2G1207). It has two homologous domains tandemly duplicated within a single polypeptide. The enzyme reacts well with 30S subunits reconstituted from 16S RNA transcripts and 30S proteins, but is almost inactive with the corresponding free RNA. E. coli RsmC is closely related to E. coli RsmD (m2G966/16S rRNA) and also to a family of other MTases from Gram-positive bacteria and Archaea, typified by the Mj0882 protein from M. jannaschii (1dus in PDB) (The acronym RsmC has also been used for for ‘Regulator of Secondary Metabolism C’, a protein not related to Ribosomal small subunit Methyltransferase C).
Phylogenomic analysis of 16S rRNA:(guanine-N2) methyltransferases suggests new family members and reveals highly conserved motifs and a domain structure similar to other nucleic acid amino-methyltransferases.