Differential inhibition of transcription from sigma(70)- and sigma(32)-dependent promoters by rifampicin

Rifampicin is an antibiotic which binds to the beta subunit of prokaryotic RNA polymerases and prevents initiation of transcription, It was found prev iously that production of heat shock proteins in Escherichia coli cells aft er a shift from 30 degrees C to 43 degrees C is not completely inhibited by this antibiotic, Here we demonstrate that while activity of a p(L)-lacZ fu sion (p(L) is a sigma(70)-dependent promoter) in E. coli cells is strongly inhibited by rifampicin, a p(groE)-lacZ fusion, whose activity is dependent on the sigma(32) factor, retains significant residual activity even at rel atively high rifampicin concentrations. Differential sensitivity to this an tibiotic of RNA polymerase holoenzymes containing either the sigma(70) or t he sigma(32) subunit was confirmed in vitro, Since the effects of an antibi otic that binds to the beta subunit can be modulated by the presence of eit her the sigma(70) or the sigma(32) subunit in the holoenzyme, it is temptin g to speculate that binding of various a factors to the core of RNA polymer ase results in different conformations of particular holoenzymes, including changes in the core enzyme. (C) 1998 Federation of European Biochemical So cieties.