Studies of the binding of Escherichia coli RNA polymerase to DNA : IV. The effect of rifampicin on binding and on RNA chain initiation

Abstract

Binding of Escherichia coli RNA polymerase to T7 DNA is not prevented by complexing of the enzyme with rifampicin, nor does rifampicin increase the rate of dissociation of the highly stable RNA polymerase holoenzyme-T7 DNA complex. Both free RNA polymerase and RNA polymerase-T7 DNA complexes are attacked by rifampicin in second-order reactions although the rate constant for the latter reaction is reduced about 100-fold. Alteration of the stability of the holoenzyme-DNA complex does not appreciably change the rate of rifampicin attack, nor does removal of sigma subunit from the RNA polymerase-DNA complex. It is suggested that the relative resistance of RNA polymerase holoenzyme-T7 DNA complexes to attack by rifampicin, when the drug is added together with the nucleoside triphosphates, is due to the rapid rate of RNA chain initiation by this complex.