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Studies on T3-induced ribonucleic acid polymerase. 3. Purification and characterization of the T3-induced ribonucleic acid polymerase from bacteriophage T3-infected Escherichia coli cells.

Abstract A procedure for the isolation and purification of bacteriophage T3-induced RNA polymerase from T3-infected Escherichia coli cells is presented. The procedure described leads to the isolation of polymerase preparation that displays a single protein band by polyacrylamide gel electrophoresis and is free of detectable ribonuclease and deoxyribonuclease activities. Other enzyme activities absent from such preparations include inorganic pyrophosphatase, nucleoside diphosphokinase, DNA polymerase, E. coli RNA polymerase, nucleoside triphosphatase, polynucleotide phosphorylase, polyriboadenylate polymerase, and polyphosphate kinase. T3-induced RNA polymerase has been characterized with regard to various biochemical parameters. The enzyme is a single polypeptide chain of molecular weight 105,000 ± 5,000. The enzyme activity is completely dependent on the presence of Mg2+, all four nucleoside triphosphates, and T3 DNA. T7 DNA shows only 2 to 5% of activity as that obtained with T3 DNA, while other native DNA preparations examined are inactive. The T3 RNA polymerase is highly sensitive to salt concentrations above 0.03 m or to reagents which react with sulfhydryl groups such as p-hydroxymercuribenzoate and N-ethylmaleimide. The enzyme catalyzes a T3 DNA-dependent 32PPi exchange into nucleoside triphosphates. However, no pyrophosphorolysis of free RNA can be demonstrated. The 32PPi exchange reaction can occur with GTP alone. The exchange reaction with the other three nucleoside triphosphates, present either alone or in combination, does not occur except when GTP is included in the reaction. The effect of E. coli RNA chain termination factor, p, on the T3 RNA polymerase reaction has been studied. It has been found that p factor has no effect on the rate, yield, or size of RNA formed in the T3 RNA polymerase-catalyzed reactions.