RNA polymerase-DNA complexes: IV. Influences of the ionic strength on the integrity of the complexes

Abstract

Dissociation of a complex of Escherichia coli RNA polymerase with DNA “keg”, which was resistant to DNAase digestion under varying ionic strength conditions was studied by gel filtration and sedimentation. This complex-like RNA polymerase lends itself to reversible dimerisation as the ionic strength of the solution varies from 0.02 to 0.1 M. Further increase in ionic strength up to 0.25–1.0 M results in dissociation of the keg into DNA and the enzyme. The relative stability of the keg in this transition range is proportional to the square root of the reciprocal of the ionic strength value. The same is valid for the dependence of the relative rate of the initiation and elongation of RNA synthesis on ionic strength. The present experiments support the hypothesis that the active form of RNA polymerase is a monomer.