Seminalplasmin is a potent inhibitor of E. coli RNA polymerase in vitro

Abstract

SEMINALPLASMIN, a protein isolated from bovine seminal plasma, specifically and almost completely inhibits synthesis of rRNA in whole Escherichia coli cells at extracellular concentrations lower than those needed for bacteriocidal action of many established antibacterial agents¹. We show here that seminalplasmin also strongly inhibits the transcription of various natural and synthetic templates by E. coli RNA polymerase in vitro, and that it does so by binding strongly to the polymerase. Seminalplasmin is, to our knowledge, the first protein isolated from an eukaryote to inhibit RNA polymerase. There is, however, a protein synthesised in E. coli following a phage infection and coded by the phage genome, which appears to inhibit E. coli RNA polymerase².