Replication of RNA viruses: I. Characterization of a viral RNA-dependent RNA polymerase

An enzyme which catalyzes the RNA-dependent synthesis of RNA from the ribonucleoside triphosphates has been purified 100-fold from extracts of Escherichia coli infected with the RNA bacteriophage f2, su-11. For this synthesis, Mg²⁺, RNA, and each of the four ribonucleoside triphosphates of adenine, uracil, guanine and cytosine are required. Bacterial ribosomal and soluble RNA and viral RNA all satisfy the requirement for RNA. The enzyme also catalyzes an exchange between inorganic pyrophosphate and ribonucleoside triphosphates in the presence of a relatively high concentration of inorganic pyrophosphate. The RNA product of the synthetic reaction has an average polymer length of at least 300 to 400 ribonucleotide units and contains each of the four different ribonucleotides in internal phosphodiester linkage. The requirements of the reaction distinguish this RNA virus RNA polymerase from other enzymes catalyzing the DNA- or RNA-dependent synthesis of RNA.