The Bacillus subtilis ywbD gene encodes RlmQ, the 23S rRNA methyltransferase forming m⁷G2574 in the A-site of the peptidyl transferase center

Identification of m⁷G at position 2574 of B. subtilis 23S rRNA using mass spectrometry. (A) MS/MS sequencing spectra of 1966.3 Da (m/z 982.63, z = 2−), sequence UAC[m⁷G]CGp, obtained from the analysis of B. subtilis WT 23S RNase H fragment after T1 digestion. Collision-induced dissociation (CID) fragmentation shows a neutral loss of 165 Da, which is specific to m⁷G and corresponds to the loss of the methylated base. (B) MS/MS sequencing spectra of 1302.2 Da (m/z 650.58, z = 2−), sequence UACGp, obtained from the analysis of B. subtilis ΔywbD 23S RNase H fragment after T1 digestion. The 3′Gp corresponds to the position 2574.