The RNA polymerase of the extremely thermophilic bacterium Thermus aquaticus T2 has been purified to homogeneity. The apparent molecular weights of the subunits of the enzyme are: 165 000, 130 000, 92 000 and 44 000. The in vitro temperature optimum of enzyme activity is around 65°C. The enzyme has a preference towards the homologous template and is strongly inhibited by KCl. Rifampicin inhibits the enzyme only to 50% even at very high concentrations. Heparin inhibits it completely, but only at higher molar excess than in the case of the Escherichia coli enzyme. The enzyme can form heparin-resistant complexes at elevated temperatures on the homologous template, but not on E. coli DNA.
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