InterPro domain: IPR002877

This entry represents FtsJ domain. RrmJ (FtsJ) is a well conserved heat shock protein present in prokaryotes, archaea, and eukaryotes. RrmJ is responsible formethylating 23 S rRNA at position U2552 in the aminoacyl (A)1-site of the ribosome [ 1 ]. U2552 is one of the five universally conserved A-loop residues and has beenshown to be methylated at the ribose 2'-OH group in the majority of organisms investigated so far. This suggests that this modification plays an important role in theA-loop function. RrmJ recognises its methylation target only when the 23 S rRNA is present in 50 S ribosomal subunits. This suggests that the RrmJ-mediated methylation must occur late in the maturation process of theribosome. This is in contrast to other known 23 S rRNA modifications that occur in earlier maturation steps.

The 1.5 A crystal structure of RrmJ in complex with its cofactor S-adenosylmethionine revealed that RrmJ has a methyltransferase fold. The active site of RrmJ appears to be formed by a catalytic triad consisting of two lysine residues and the negatively charged aspartate residue. Another highly conserved glutamate residue that is present in the active site of RrmJ appears to play only a minor role in the methyltransfer reaction in vivo [ 2 ].

1. Overexpression of two different GTPases rescues a null mutation in a heat-induced rRNA methyltransferase. J. Bacteriol. 184, 2692-8
2. RNA methylation under heat shock control. Mol. Cell 6, 349-60