期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1972
卷号：69
期号：5
页码：1100-1103
DOI：10.1073/pnas.69.5.1100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：DNA from a transducing bacteriophage carrying a fusion of the tryptophan and lactose operons of E. coli ({lambda}dtrp-lac) has been used to direct cell-free synthesis of {beta}-galactosidase (EC 3.2.1.23 ). Whereas normal lac operon ({lambda}dlac) 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.
