title: Functional mutants of phenylalanine transfer RNA from Escherichia coli.
abstract: The gene pheV from Escherichia coli, coding for tRNAPhe and carried on a plasmid, has been mutagenised with hydroxylamine. Mutants in the structural gene have been identified using two criteria: (i) de-attenuation of beta-galactosidase expression, while under the control of the attenuator region of the pheS,T operon by means of an operon fusion; (ii) loss of ability to complement thermosensitivity of a mutant Phe-tRNA synthetase. Mutants showing de-attenuation were sequenced and two nucleotide changes identified: G44----A44 (found five times) and m7G46----A46 (found once). Sequencing of mutants that lost complementation identified two further tRNA mutants, C2---U2 and G15----A15; the mutant m7G46----A46 was also re-isolated by this criterion. Three of the mutants involve bases implicated in tertiary rather than secondary structure hydrogen bonding. One hypothesis for the mechanism of de-attenuation is that mutant tRNAPhe molecules compete with the wild-type tRNAPhe on the ribosome but are inefficient at some step in the elongation process.
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005809:Genes, Regulator; D009154:Mutation; D009690:Nucleic Acid Conformation; D010649:Phenylalanine; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000235:genetics*; D013329:Structure-Activity Relationship
chemical_list: D010649:Phenylalanine; D012343:RNA, Transfer