T. Caldas et al., The FtsJ/RrmJ heat shock protein of Escherichia coli is a 23 S ribosomal RNA methyltransferase, J BIOL CHEM, 275(22), 2000, pp. 16414-16419
Ribosomal RNAs undergo several nucleotide modifications including methylati
on. We identify FtsJ, the first encoded protein of the ftsJ-hflB heat shock
operon, as an Escherichia coli methyltransferase of the 23 S rRNA. The met
hylation reaction requires S-adenosylmethionine as donor of methyl groups,
purified FtsJ or a S-150 supernatant from an FtsJ-producing strain, and rib
osomes from an FtsJ-deficient strain. In vitro, FtsJ does not efficiently m
ethylate ribosomes purified from a strain producing FtsJ, suggesting that t
hese ribosomes are already methylated in vivo by FtsJ. FtsJ is active on ri
bosomes and on the 50 S ribosomal subunit, but is inactive on free rRNA sug
gesting that its natural substrate is ribosomes or a pre-ribosomal ribonucl
eoprotein particle. We identified the methylated nucleotide as 2'-O-methylu
ridine 2552, by reverse phase high performance liquid chromatography analys
is, boronate affinity chromatography, and hybridization-protection experime
nts. In view of its newly established function, FtsJ is renamed RrmJ and it
s encoding gene, rrmJ.