The gene for 16S rRNA methyltransferase (ksgA) functions as a multicopy suppressor for a cold-sensitive mutant of era, an essential RAS-like GTP-binding protein in Escherichia coli.
Era, a Ras-like GTP-binding protein in Escherichia coli, has been shown to be essential for growth. However, its cellular functions still remain elusive. In this study, a genetic screening of an E. coli genomic library was performed to identify those genes which can restore the growth ability of a cold-sensitive mutant, Era(Cs) (E200K), at a restrictive temperature when expressed in a multicopy plasmid. Among eight suppressors isolated, six were located at 1 min of the E. coli genomic map, and the gene responsible for the suppression of Era(Cs) (E200K) was identified as the ksgA gene for 16S rRNA transmethylase, whose mutation causes a phenotype of resistance to kasugamycin, a translation initiation inhibitor. This is the first demonstration of suppression of impaired function of Era by overproduction of a functional enzyme. A possible mechanism of the suppression of the Era cold-sensitive phenotype by KsgA overproduction is discussed.
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Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Inouye
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D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003080:Cold Temperature; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D020558:GTP Phosphohydrolases / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D016153:Genes, Suppressor / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics*; D009154:Mutation; D016601:RNA-Binding Proteins
D029968:Escherichia coli Proteins; D016601:RNA-Binding Proteins; C068027:era protein, E coli; D008780:Methyltransferases; C047346:16S rRNA (adenine(1518)-N(6)-adenine(1519)-N(6))-dimethyltransferase; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins