Biosynthesis of RNA polymerase in Escherichia coli: IV. Accumulation of intermediates in mutants defective in the subunit assembly

Abstract

In a series of attempts to elucidate the control system which operates in the formation of the DNA-dependent RNA polymerase in Escherichia coli, the pathway of subunit assembly in vivo was further investigated by a detailed analysis of the distribution of pulse-labelled subunit proteins in cell extracts of the wild type as well as assembly-defective mutant strains. Two distinct types of the assembly-defective mutants were found, which carry temperature-sensitive lethal mutations in the gene encoding the β′ subunit of RNA polymerase. One of the mutants (strain TIn a series of attempts to elucidate the control system which operates in the formation of the DNA-dependent RNA polymerase in Escherichia coli, the pathway of subunit assembly in vivo was further investigated by a detailed analysis of the distribution of pulse-labelled subunit proteins in cell extracts of the wild type as well as assembly-defective mutant strains. Two distinct types of the assembly-defective mutants were found, which carry temperature-sensitive lethal mutations in the gene encoding the β′ subunit of RNA polymerase. One of the mutants (strain TIn a series of attempts to elucidate the control system which operates in the formation of the DNA-dependent RNA polymerase in Escherichia coli, the pathway of subunit assembly in vivo was further investigated by a detailed analysis of the distribution of pulse-labelled subunit proteins in cell extracts of the wild type as well as assembly-defective mutant strains. Two distinct types of the assembly-defective mutants were found, which carry temperature-sensitive lethal mutations in the gene encoding the β′ subunit of RNA polymerase. One of the mutants (strain TIn a series of attempts to elucidate the control system which operates in the formation of the DNA-dependent RNA polymerase in Escherichia coli, the pathway of subunit assembly in vivo was further investigated by a detailed analysis of the distribution of pulse-labelled subunit proteins in cell extracts of the wild type as well as assembly-defective mutant strains. Two distinct types of the assembly-defective mutants were found, which carry temperature-sensitive lethal mutations in the gene encoding the β′ subunit of RNA polymerase. One of the mutants (strain Ts4) accumulates the intermediate subassembly, α2β complex, while another mutant (strain T16) appears to have a defect in the final step of core enzyme formation leading to accumulation of the premature core enzyme.) accumulates the intermediate subassembly, α2β complex, while another mutant (strain T16) appears to have a defect in the final step of core enzyme formation leading to accumulation of the premature core enzyme.) accumulates the intermediate subassembly, α2β complex, while another mutant (strain T16) appears to have a defect in the final step of core enzyme formation leading to accumulation of the premature core enzyme.) accumulates the intermediate subassembly, α2β complex, while another mutant (strain T16) appears to have a defect in the final step of core enzyme formation leading to accumulation of the premature core enzyme. The subassemblies accumulated in these mutants were suggested to be degraded rapidly and preferentially. The mutants synthesize subunit proteins at increased rates; this seems to compensate the inefficient assembly as well as the rapid degradation.