Partial purification and properties of calf thymus deoxyribonucleic acid dependent RNA polymerase III

DNA-dependent RNA polymerase III (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.-7.6) has been isolated and partially purified from calf thymus tissue. Significant amounts of enzyme III are present in this tissue (up to 15% of the total activity of thymus homogenates). This enzyme has been characterized with respect to its chromatographic properties, broad ammonium sulfate optimum (0.04-0.2 M), template requirements, divalent metal optima, and its unique alpha-amanitin sensitivity (50% inhibition of activity occurring at an alpha-amanitin concentration of 10 mug/ml).