Dissociation of DNA-dependent RNA-polymerase from E. coli in lithium chloride

Affinity labeling of a cysteine at or near the catalytic center of Escherichia coli B DNA-dependent RNA polymerase

9-beta-D-Arabinofuranosyl-6-thiopurine was used to affinity label DNA-dependent RNA polymerase isolated from Escherichia coli B. This substrate analogue displayed competitive type inhibition which could be reversed by addition of a thiol reagent, such as dithiothreitol, while exposure to hydrogen peroxide, a mild oxidizing agent, caused an increase in both the inhibitory and enzyme binding capability of arabinofuranosyl thiopurine. Chromatographic analysis of the products obtained by pronase digestion of the 9-beta-D-arabinofuranosyl-6-[35S]thiopurine-enzyme complex suggests that disulfide bond formation occurs between the inhibitor and a cysteine residue located in or near the active center of the enzyme. In addition, polyacrylamide gel electrophoresis indicated that the arabinofuranosyl thiopurine moeity was bound to the beta' subunit of the enzyme.

Multiple effects of an RNA polymerase beta' mutation on in vitro transcription

S. tyrphimurium strain BY324 is temperature sensitive due to a mutation (rpo C32) in the gene for the RNA polymerase beta' subunit. Transcription of T7 DNA by RNA polymerase purified from this strain is temperature sensitive in vitro. The enzyme is slightly defective in template binding and RNA chain initiation, but the major defect is in RNA chain elongation. The rate of RNA chain elongation is reduced 4-5 fold relative to wild-type. RNA chain termination does not appear to be affected by the beta' mutation. While the elongation defect is suppressed by glycerol or dimethylsulfoxide, the initiation defect is not. Possible roles for the beta' subunit in enzyme function are discussed in light of these results.

Conversion of Escherichia coli RNA polymerase to a template independent enzyme

Preparations of RNA polymerase (E.C.2.7.7.6) from uninfected Escherichia coli, T4 infected Escherichia coli, and Acinetobacter calcoaceticus when centrifuged in sucrose gradients in the absence of magnesium ions gave rise to five peaks, all of which were able to form polymers from ribonucleoside 5'-triphosphates in the absence of template or primer. All of the peaks obtained from the Escherichia coli enzyme appeared to contain the subunit alpha and beta and, in addition, polypeptides which appeared to be derived from the subunit beta.

Rapid isolation of highly active RNA polymerase from Escherichia coli and its subunits by matrix-bound heparin

1. RNA polymerase from Escherichia coli is selectively and strongly retained by a heparin-substituted agarose and can be eluted therefrom by a neutral buffer containing 0.6 M salt. The method is applicable to relatively crude preparations of the enzyme on a preparative scale giving highly purified RNA polymerase in excellent yield. The enzyme obtained by this procedure shows the highest specific activity so far reported and is pure and enriched in factor sigma as indicated by dodecylsulfate gel electrophoresis. 2. Based on the differential affinity of the subunits of the enzyme for the heparin-carrying gel matrix, a method for separation of alpha, beta' + beta and sigma subunits by application of urea and salt-containing buffers is described. Upon recombination and dialysis with urea-free buffer 40-50% of the enzyme activity is restored.