TheBacillus subtilis ywbDgene encodes RlmQ, the 23S rRNA methyltransferase forming m7G2574 in the A-site of the peptidyl transferase center

Abstract

Ribosomal RNA contains many posttranscriptionally modified nucleosides, particularly in the functional parts of the ribosome. The distribution of these modifications varies from one organism to another. InBacillus subtilis, the model organism for Gram-positive bacteria, mass spectrometry experiments revealed the presence of 7-methylguanosine (m7G) at position 2574 of the 23S rRNA, which lies in the A-site of the peptidyl transferase center of the large ribosomal subunit. Testing several m7G methyltransferase candidates allowed us to identify the RlmQ enzyme, encoded by theywbDopen reading frame, as the MTase responsible for this modification. The enzyme methylates free RNA and not ribosomal 50S or 70S particles, suggesting that modification occurs in the early steps of ribosome biogenesis.