A temperature-sensitive mutation in Escherichia coli transfer RNA.

摘要: Abstract Mutants that grow at 42 °C only in the presence of added transfer RNA (temperature-sensitive tRNA-dependent strains) were isolated from an RNA-permeable strain Escherichia coli after mutagenesis with N -methyl- N′ -nitro- -nitrosoguanidine. One mutant has been studied some detail. The observed reversion frequency 10 −7 to 2 × −6 implies mutation is a single event. Growth and its capacity induce β-galactosidase arrested within minutes cultures shifted 30 °C. half-lives for degradation pulse-labelled RNA, rifampicin addition, comparable °C; extracted polysomes smaller incubated briefly In vitro protein synthesis using extract showed absolute temperature sensitivity, testing polyphenylalanine polyproline synthesis, isoleucine incorporation poly(U) streptomycin. This activity was completely restored by addition tRNA parental but not mutant. Similar results obtained use tRNA-depleted wild-type strain. Thermal inactivation reactivated when extracts returned slightly elevated magnesium concentrations. These indicate this undergone structural change many molecules, leading reversible temperaturesensitive lesion.