Solubilization and characterization of RNA polymerase from a higher plant

RNA polymerase has been solubilized from sugar beet chromatin. With calf thmus or sugar beet DNA as template enzyme activity was linear with respect to protein concentration and required the presence of all four nucleoside triphospahates, added DNA and divalent metal ions. The enzyme exhibited a sharp Mn²⁺ optimum of 1·25 mM and a Mg²⁺ optimum at 10mM. The Mn²⁺/Mg²⁺ activity ratio (activity at optimum concentrations) was 2·0 with an optimum salt concentration of 50 mM. Based on data including inhibition with α-amanitin (0·025 μg/ml), the majority of the total activity appeared to be RNA polymerase I. Subsequent fractionation by DEAE-Sephadex column chromatography resulted in one peak of activity eluted with 0·18 M (NH₄)₂SO₄.