Identification of therrmAGene Encoding the 23S rRNA m1G745 Methyltransferase inEscherichia coliand Characterization of an m1G745-Deficient Mutant

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Abstract
AnEscherichia colimutant lacking the modified nucleotide m1G 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 m1G 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. TherrmAgene encoding 23S rRNA m1G745 methyltransferase was mapped to bp 1904000 on theE. colichromosome and identified to be identical to the previously sequenced geneyebH.