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：1973
卷号：70
期号：2
页码：334-338
DOI：10.1073/pnas.70.2.334
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have studied the in vitro repression of gal mRNA synthesis by the gal repressor from Escherichia coli. By use of a four-step purification procedure involving chromatography on phosphocellulose, DEAE-cellulose, and an affinity resin, the gal repressor has been purified about 1600-fold from a crude cell extract. The purification was aided by use of a cell extract made after prophage induction of cells lysogenic for bacteriophage {lambda} that carries the gal repressor gene (galR). The highly purified gal repressor is an effective and specific repressor of in vitro synthesis of gal mRNA with {lambda} gal DNA as template. Both D-fucose and D-galactose overcome the action of gal repressor; the half-maximal concentrations of D-fucose and D-galactose for overcoming the action of repressor are 1 mM and 0.5 mM, respectively. The repressor fails to repress gal-specific transcription when the gal DNA contains a cis-dominant operator constitutive (Oc) mutation. We conclude that the gal repressor recognizes the gal operator site and acts by preventing gal transcription.
