Interaction of a new polypeptide with yeast RNA polymerase B.

A basic 37,000-dalton protein (P37), purified from yeast cells, interacts with yeast RNA polymerase B and drastically increases its specific activity. A complex of P37 and RNA polymerase can be isolated by sedimentation through a glycerol gradient. The complex is dissociated at the ionic strength of 0.9. The preferential binding of P37 with RNA polymerase form BI (with the unproteolyzed B220 subunit) was visualized by polyacrylamide gel electrophoresis under nondenaturing conditions. Kinetic analysis of the RNA polymerase cofactor interaction indicated that the dissociation constant for the complex is 5 X 10(-8) M.