Azotobacter vinelandii RNA polymerase. VII. Enzyme transitions during unprimed r[I-C] synthesis.

Transitions in the state of RNA polymerase were demonstrated during the unprimed synthesis of the r[I-C] copolymer. No detectable change in the usual dimer-monomer pattern was noted during the lag phase (0-25 min at 37 degrees ) after analysis of the reaction mixture by acrylamide gel electrophoresis. At the end of the lag phase, a major alteration in the electrophoretic pattern occurred, marked by the disappearance of the dimer-monomer bands and the concomitant appearance of a series of monomer-r[I-C] copolymer complexes. As these complexes of r[I-C] copolymer with one or more polymerase monomer were formed, an enzymatically inactive component (gamma protein) of the polymerase was displaced. During the phase of rapid r[I-C] copolymer synthesis, the active form of the A. vinelandii RNA polymerase was the r[I-C] monomer lacking the gamma protein.