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Translation of the UGA triplet in vitro by tryptophan transfer RNA's

1971; Elsevier BV; Volume: 58; Issue: 2 Linguagem: Inglês

10.1016/0022-2836(71)90363-9

1089-8638

David Hirsh, Lawrence M. Gold,

Bacteriophages and microbial interactions

Tryptophan transfer RNA from the UGA-suppressing strain of Escherichia coli CAJ64 was purified and assayed for suppressor activity in vitro in two ways: by translation of the bacteriophage T4 lysozyme messenger RNA bearing a UGA mutation, and by translation of poly(U-G-A). Purified tRNATrp, and no other fraction, stimulates lysozyme synthesis 30-fold above the level seen when comparable amounts of tryptophan tRNA from the non-suppressing strain, CA244, were added; it also translates poly(U-G-A) as polytryptophan more efficiently than the su− tRNA. Tryptophan tRNA from the non-suppressing strain is active in the assays but far less so than CAJ64 tRNATrp, and this is consistent with the leakiness of su− strains. Since the nucleotide sequences of these tryptophan tRNA's are known (Hirsh, 1971), it is concluded that tRNA with a CCA anticodon recognizes the UGA triplet and this recognition is improved by a nucleotide change elsewhere in the molecule.