title: In vitro synthesis of the first dipeptide of the beta subunit of Escherichia coli RNA polymerase.
abstract: Plasmids pNF1337 and pNF1341, which contain part of the L10 operon including the RNA polymerase beta-subunit gene, have been used as templates in vitro to investigate expression of the beta-subunit gene. For these studies, the synthesis of the first dipeptide of the beta subunit, fMet-Val, was measured instead of that of the entire protein. By using this dipeptide system, we studied the effects of RNA polymerase holoenzyme and L factor (nus A gene product) on fMET-Val synthesis and compared the relative effects of the primary and secondary promoters in the L10 operon on expression of the beta-subunit gene. The results show that the inhibitory effect of RNA polymerase on beta-subunit synthesis and the stimulatory effect of L factor occur before formation of the first dipeptide bond. In this in vitro system, the secondary promoters account for about 50% of the total fMet-Val synthesized. Although the primary promoter is sensitive to guanosine 5'-diphosphate 3'-diphosphate in vitro, the secondary promoters are not affected by this nucleotide.
mesh_terms: D001426:Bacterial Proteins / Q000494:pharmacology; D002474:Cell-Free System; D004269:DNA, Bacterial / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis* / Q000494:pharmacology; D004151:Dipeptides / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology; D005786:Gene Expression Regulation / Q000187:drug effects; D046911:Macromolecular Substances; D009876:Operon; D010957:Plasmids
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004151:Dipeptides; D046911:Macromolecular Substances; D012321:DNA-Directed RNA Polymerases