A MINOR ARGININE TRANSFER-RNA MUTANT LIMITS TRANSLATION PREFERENTIALLY OF A PROTEIN DEPENDENT ON THE COGNATE CODON

The Escherichia coli argU gene encodes a rare arginine tRNA (anticodon UCU) that translates the similarly rare AGA codon. The argU10(Ts) mutation is a transition that changes the first nucleotide of the mature tRNA from G to A, presumably destabilizing the acceptor stem. This mutation, when present in haploid condition in the chromosome, reduces the growth rate at 30°C and results in cessation of growth after 60 to 90 min at 43°C. The mutation also preferentially limits (compared with total protein synthesis) translation of an induced gene that depends on five AGA codons, i.e., the λ cI repressor gene. Translation of another inducible protein, β-galactosidase, which does not involve AGA codons, was inhibited to a much lesser extent. The chromosomal argU(Ts) mutation also confers the Pin phenotype, that is, loss of ability of the host, as a P2 lysogen, to inhibit growth of bacteriophage λ, probably the result of reduced translation of the P2 old gene, which contains five AGA codons (E. Haggard-Ljungquist, V. Barreiro, R. Calendar, D.M. Kurnit, and H. Cheng, Gene 85:25-33, 1989).