RsmJ catalyzes formation of m2G1516 in the loop of hairpin 45 at the 3’-end of 16S ribosomal RNA. Recombinant RsmJ specifically methylates 30S subunits extracted from the deletion strain. All ribosomal guanine-(N2)-methyltransferases have similar AdoMet-binding sites. Moreover, comparative sequence analysis supported by sequence/structure threading suggests that rRNA:m2G MTases are very closely related to RNA and DNA:m6A MTases and that these two enzyme families share common architecture of the active site and presumably a similar mechanism of methyl group transfer onto the exocyclic amino group of their target bases.
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.