Small reovirus-specific particle with polycytidylate-dependent RNA polymerase activity.
We previously reported that virus-specific particles with polycytidylate [poly(C)]-dependent RNA polymerase activity accumulated at 30 degrees C in reovirus-infected cells. These particles sedimented heterogeneously from 300 to 550S and traversed through a 40% glycerol cushion to the pellet in 3 h at 190,000 x g. In the present report, we found that smaller particles with poly(C)-dependent RNA polymerase activity remained in the glycerol cushion. These smaller, enzymatically active particles, when purified, sedimented at 15 to 1S. They were spherical or triangular with a diameter of 11 to 12 nm. They were comprised mostly, and likely solely, of one reovirus protein, sigma NS. No particles with poly(C)-dependent RNA polymerase activity were found in mock-infected cells. Chromatography on the cation exchanger, CM-Sephadex, ascertained that sigma NS was the poly(C)-dependent RNA polymerase and showed its existence in two forms. In one form, it was enzymatically active and eluted from the column at 0.5 M KCl. In the enzymatically inactive state, it did not bind to the column. Our results suggest that the enzymatically active form of sigma NS carries a greater net positive charge than the inactive form. They also suggest that both forms of sigma NS are associated with a particle which has poly(C)-dependent RNA polymerase activity.
D000818:Animals; D002499:Centrifugation, Density Gradient; D012321:DNA-Directed RNA Polymerases / Q000302:isolation & purification / Q000378:metabolism*; D007739:L Cells; D012089:Mammalian orthoreovirus 3 / Q000032:analysis / Q000201:enzymology*; D051379:Mice; D011066:Poly C / Q000494:pharmacology; D011487:Protein Conformation; D012087:Reoviridae / Q000201:enzymology*; D014764:Viral Proteins / Q000302:isolation & purification*
D014764:Viral Proteins; D011066:Poly C; D012321:DNA-Directed RNA Polymerases