Azotobacter vinelandii Ribonucleic Acid Polymerase

Abstract r(G-C)n is the alternating copolymer of guanylic and cytidylic residues synthesized in an RNA polymerase-catalyzed reaction in which r(I-C)n or d(I-C)n copolymer serves as template. When r(I-C)n copolymer serves as template, synthesis of r(G-C)n occurs at a rate approximately 20% that found for r(I-C)n-directed r(I-C)n synthesis. Net synthesis of r(G-C)n can be obtained in an r(I-C)n-directed reaction, but separation of r(I-C)n template and r(G-C)n product is difficult and results in poor yields of purified r(G-C)n. r(G-C)n is incapable of serving as template for r(I-C)n or r(G-C)n synthesis; in fact, r(G-C)n inhibits unprimed r(I-C)n synthesis. Any synthesis of r(I-C)n found in a reaction mixture in which r(G-C)n is being tested for template activity can be attributed to the presence of small amounts of r(I-C)n contaminating the r(G-C)n preparation. r(I-C)n-directed r(G-C)n synthesis is supported by Mn++ or Mg++, and the rate of synthesis drops sharply with temperature.