Modomics - A Database of RNA Modifications

Full name: Ribosomal RNA small subunit methyltransferase A
Synonym: KsgA, JW0050
GI: 125699
Orf: b0051
COG: COG0030
UniProt: P06992
Structures: | 1QYR | 3TPZ | 4ADV |
Enzyme type: methyltransferase
Position of modification - modification: s:1518(1518) - m6,6A
s:1519(1519) - m6,6A


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).

Protein sequence:


Enzymatic activities:

Reaction Substrate Type Position
A:m6A rRNA (r) SSU/16S/prokaryotic cytosol 1518
m6A:m6,6A rRNA (r) SSU/16S/prokaryotic cytosol 1518
A:m6A rRNA (r) SSU/16S/prokaryotic cytosol 1519
m6A:m6,6A rRNA (r) SSU/16S/prokaryotic cytosol 1519


Title Authors Journal Details PubMed Id DOI
Structural insights into methyltransferase KsgA function in 30S ribosomal subunit biogenesis. Boehringer D, O'Farrell HC, Rife JP, Ban N J Biol Chem [details] 22308031 -
Site-directed mutants of 16S rRNA reveal important RNA domains for KsgA function and 30S subunit assembly. Desai PM, Culver GM, Rife JP Biochemistry [details] 21142019 -
Mechanistic insight into the ribosome biogenesis functions of the ancient protein KsgA. Connolly K, Rife JP, Culver G Mol Microbiol [details] 18990185 -
Control of substrate specificity by a single active site residue of the KsgA methyltransferase. O'Farrell HC, Musayev FN, Scarsdale JN, Rife JP Biochemistry [details] 22142337 -
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. Poldermans B, Roza L, Van Knippenberg PH J Biol Chem [details] 383712 -
Studies on the function of two adjacent N6,N6-dimethyladenosines near the 3' end of 16S ribosomal RNA of Escherichia coli. IV. The effect of the methylgroups on ribosomal subunit interaction. Poldermans B, Bakker H, Van Knippenberg PH Nucleic Acids Res [details] 6986611 -
Crystal structure of KsgA, a universally conserved rRNA adenine dimethyltransferase in Escherichia coli. O'Farrell HC, Scarsdale JN, Rife JP J Mol Biol [details] 15136037 -

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