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Subunit assembly and metabolic stability of E. coli RNA polymerase
Author(s) -
Ishihama Akira,
Fujita Nobuyuki,
Glass Robert E.
Publication year - 1987
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340020106
Subject(s) - polymerase , rna polymerase , biology , microbiology and biotechnology , protein subunit , rna , rna dependent rna polymerase , rpob , biochemistry , specificity factor , enzyme , gene , 16s ribosomal rna
Immunological cross‐reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase genered both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, β and β′, and the two small and intact subunits, α and σ. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state. Using this method, degradation in vivo was found for some, but not all, of the amber fragments of β subunit in merodiploid cells carrying both wild‐type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli , degradation of the full‐sized subunits was found in two cases, i.e., several temperature‐sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary‐phase cells of a wild‐type E. coli . The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure.