Partial purification of mitochondrial RNA polymerase from rat liver.

Mitochondrial RNA polymerase activity from rat liver has previously been demonstrated in intact organelles. This activity has now been solubilized, partially purified, and shown to be a true polymerase, free of nuclease. The enzyme is derived from mitochondria and is not from contaminating bacteria or nuclear components. The enzyme is distinguished from its nuclear counterparts by its behavior on ammonium sulfate fractionation and lack of inhibition by alpha-amanitin. Rifamycin inhibits the crude enzyme, but only inconsistently inhibits the more purified preparation.