Isolation and partial characterization of three Escherichia coli mutants with altered transfer ribonucleic acid methylases

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology



Document Type


Medical Subject Headings

Chromatography, Affinity; Chromatography, Thin Layer; Chromosome Mapping; Electrophoresis; Escherichia coli; Genes; Guanosine; Methyltransferases; Mutagens; *Mutation; Nitrosoguanidines; RNA, Bacterial; RNA, Ribosomal; RNA, Transfer; Recombination, Genetic; S-Adenosylmethionine; Thymidine; Uridine


Seven transfer ribonucleic acid (tRNA) methylase mutants were isolated from Escherichia coli K-12 by examining the ability of RNA prepared from clones of unselected mutagenized cells to accept methyl groups from S-adenosylmethionine catalyzed by crude enzymes from wild-type cells. Five of the mutants had an altered uracil-tRNA methylase; consequently their tRNA's lacked ribothymidine. One mutant had tRNA deficient in 7-methylguanosine, and one mutant contained tRNA lacking 2-thio-5-methylaminomethyluridine. The genetic loci of the three tRNA methylase mutants were distributed over the E. coli genome. The mutant strain deficient in 7-methylguanosine biosynthesis showed a reduced efficiency in the suppression of amber mutations carried by T4 or lambda phages.

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Citation: J Bacteriol. 1975 Apr;122(1):257-65.

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