This is the N-terminal domain of the RsmF methyl transferase. RsmF is a multi-site-specific methyltransferase that is responsible for the synthesis of three modifications on cytidines in 16S ribosomal RNA. The N-terminus is critical for stabilising the catalytic core of the enzyme [1].

1: The structure of the RNA m5C methyltransferase YebU from Escherichia coli reveals a C-terminal RNA-recruiting PUA domain. Hallberg BM, Ericsson UB, Johnson KA, Andersen NM, Douthwaite S, Nordlund P, Beuscher AE 4th, Erlandsen H; J Mol Biol. 2006;360:774-787. PMID:16793063

2: Multi-site-specific 16S rRNA methyltransferase RsmF from Thermus thermophilus. Demirci H, Larsen LH, Hansen T, Rasmussen A, Cadambi A, Gregory ST, Kirpekar F, Jogl G; RNA. 2010;16:1584-1596. PMID:20558545