RsmA (formerly KsgA) dimethylates two very conserved adjacent adenosines (positions 1518 and 1519) in the loop of a conserved hairpin h45 near the 3′-end of 16S rRNA. RsmA recognizes its substrate adenosine residues only in the context of a near mature 30S subunit and is required for the efficient processing of the rRNA termini during ribosome biogenesis dual function). AdoMet is the methyl group donor. RsmA (Dim1p) is the yeast ortholog. They belong to the erm family of methyltransferase responsible for erythromycin resistance. Notice, the acronym RsmA has also been used for for Regulator of Secondary Metabolism A, a protein not related to the RNA small subunit Methyltransferase. Structure of the E. coli methyltransferase RsmA bound to the E. coli 30S ribosomal subunit was solved (4ADV).
Studies on the function of two adjacent N6,N6-dimethyladenosines near the 3' end of 16 S ribosomal RNA of Escherichia coli. III. Purification and properties of the methylating enzyme and methylase-30 S interactions.