title: Recombinant Escherichia coli RNA polymerase: purification of individually overexpressed subunits and in vitro assembly.
abstract: New improved methods were developed for the purification to apparent homogeneity of alpha, beta, beta', and sigma subunits of Escherichia coli RNA polymerase (RNAP) from corresponding overproducing strains. The purified subunits were assembled into enzymatically active RNAP holoenzyme (alpha 2 beta beta' sigma) using the optimal subunit molar ratio (alpha:beta:beta':sigma = 2:8:4:1) at a total protein concentration of 0.5 mg/ml. The presence of sigma subunit and 10 microM ZnCl2 in the reconstitution mixture increased the yield of RNAP approximately 4 times. The assembled RNA polymerase was purified by two successive chromatographic steps using size-exclusion Superose 6 and anion exchange Mono Q FPLC columns, which resulted in the electrophoretically homogeneous holoenzyme with overall yield of 56%. The specific activity of the recombinant RNAP estimated by the standard T4 transcription assay was 6.5 nmol of [3H]UTP incorporated into acid-insoluble RNA product per microgram of RNAP per 1 h.
authors.affiliation: Public Health Research Institute, New York, New York 10016.
authors.forename: S
authors.initials: S
authors.lastname: Borukhov
authors.forename: A
authors.initials: A
authors.lastname: Goldfarb
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D001709:Biotechnology / Q000379:methods; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D011487:Protein Conformation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D012808:Sigma Factor / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D012808:Sigma Factor; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases