BglG, the transcriptional antiterminator of the bgl system, interacts withthe beta ' subunit of the Escherichia coli RNA polymerase

The Escherichia coil BglG protein antiterminates transcription at two termi nator sites within the bgl operon in response to the presence of P-glucosid es in the growth medium. BglG was previously shown to be an RNA-binding pro tein that recognizes a specific sequence located just upstream of each of t he terminators and partially overlapping with them. We show here that BglG also binds to the E. coli RNA polymerase, both in vivo and in vitro. By usi ng several techniques, we identified the beta subunit of RNA polymerase as the target for BglG binding. The region that contains the binding site for BglG was mapped to the N-terminal region of beta. The beta subunit, produce d in excess, prevented BglG activity as a transcriptional antiterminator. P ossible roles of the interaction between BglG and the polymerase beta subun it are discussed.