title: Detection and isolation of the repressor protein for the tryptophan operon of Escherichia coli.
abstract: DNA from a transducing bacteriophage carrying a fusion of the tryptophan and lactose operons of E. coli (lambdadtrp-lac) has been used to direct cell-free synthesis of beta-galactosidase (EC 3.2.1.23). Whereas normal lac operon (lambdadlac) DNA requires adenosine-3':5'-cyclic monophosphate (cAMP) for beta-galactosidase synthesis, trp-lac DNA is unaffected by cAMP. This difference in cAMP dependence verifies the presence of a cAMP-requiring promoter in the lac operon that has been removed from the trp-lac DNA. Synthesis with trp-lac DNA is controlled by the protein product of the tryptophan repressor gene (trpR). Synthesis in extracts of trpR(-) (repressor-negative) cells is progressively reduced by increased additions of extract from trpR(+) cells. No trpR(-) product repression is seen when beta-galactosidase synthesis is programmed by normal lac DNA. This highly sensitive and specific assay has facilitated quantitation and partial purification of the trp repressor.
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification*; D002474:Cell-Free System; D003090:Coliphages / Q000032:analysis / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D004269:DNA, Bacterial / Q000378:metabolism; D004279:DNA, Viral / Q000378:metabolism; D004926:Escherichia coli / Q000032:analysis / Q000201:enzymology / Q000378:metabolism*; D005696:Galactosidases / Q000096:biosynthesis; D005809:Genes, Regulator; D005815:Genetic Code; D005838:Genotype; D007785:Lactose / Q000096:biosynthesis; D009876:Operon; D014161:Transduction, Genetic; D014364:Tryptophan / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004279:DNA, Viral; D014364:Tryptophan; D000242:Cyclic AMP; D005696:Galactosidases; D007785:Lactose