Identification of the rrmA Gene Encoding the 23S rRNA m(1)G745 Methyltransferase in Escherichia coli and Characterization of an m(1)G745-Deficient Mutant

An Escherichia coli mutant lacking the modified nucleotide m(1)G in rRNA has previously been isolated (G. R. Björk and L. A. Isaksson, J. Mol. Biol. 51:83–100, 1970). In this study, we localize the position of the m(1)G to nucleotide 745 in 23S rRNA and characterize a mutant deficient in this modification. This mutant shows a 40% decreased growth rate in rich media, a drastic reduction in loosely coupled ribosomes, a 20% decreased polypeptide chain elongation rate, and increased resistance to the ribosome binding antibiotic viomycin. The rrmA gene encoding 23S rRNA m(1)G745 methyltransferase was mapped to bp 1904000 on the E. coli chromosome and identified to be identical to the previously sequenced gene yebH.