title: nusB: a protein factor necessary for transcription antitermination in vitro by phage lambda N gene product.
abstract: We demonstrate that the protein product of the Escherichia coli nusB gene is essential for transcription antitermination in vitro by phage lambda N gene product. We recently have described a convenient biochemical assay for N protein activity in the S30-coupled transcription translation system and demonstrated that N action requires the 69-kDa L factor (nusA), the product of E. coli nusA gene. Using a complementation assay for the restoration of N activity specifically in the nusB mutant extract, we have purified the nusB complementing activity. This activity is due to a 15-kDa polypeptide that is overproduced in E. coli containing multiple copies of the nusB gene. We find that nusA and nusB are required for N activity to suppress a rho-dependent as well as a rho-independent terminator. The requirement for nusB protein in antitermination could not be overcome by an excess of nusA or N protein, nor could an excess of nusB overcome the requirements for nusA in antitermination. Our results suggest that the formation of an antitermination apparatus by N requires nusA and nusB proteins in equimolar amounts.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D010582:Bacteriophage lambda / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors; D014764:Viral Proteins