Poliovirus-infected HeLa cells were labeled with radioactive methionine or phenylalanine and subjected to a new purification procedure for the viral induced RNA polymerase activity. Detergent-solubilized polymerase activity was purified by precipitation with 2 M LiCl and sedimentation through sucrose gradients. Approximately 0.001% of the incorporated amino acid radio-activity sediments with the peak of polymerase activity. Gradient fractions comprising the polymerase activity peak were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and found to contain predominantly one virus-specific polypeptide. Polyacrylamide gel electrophoresis also reveals that this purified polypeptide migrates with a 58,000 molecular weight noncapsid polio-virus polypeptide.
