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标题：Multiple Regulation of Galactose Operon—Genetic Evidence for a Distinct Site in the Galactose Operon that Responds to capR Gene Regulation in Escherichia coli K-12
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作者：Sui-Sheng Hua ; Alvin Markovitz
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：1974
卷号：71
期号：2
页码：507-511
DOI：10.1073/pnas.71.2.507
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Previous results demonstrated that the capR (lon) locus, which is not linked to the gal operon, independently controls the synthesis of the gal operon enzymes and gal mRNA, i.e., galO+capR9 strains are derepressed 4- to 6-fold as compared to galO+capR+ strains. A mutation has been isolated and localized in the galactose operator region that defines a new and distinct site of control. Mutation in this site, designated galOcapR+, causes a 4-fold increase in the galactose enzymes, galactokinase (EC 2.7.1.6 ) and UDP-galactose-4-epimerase (EC 5.1.3.2 ), in a capR+ background. These mutants exhibit a reduced response to regulation by the unlinked regulator gene capR (lon). However, the galOcapR+ mutants are still subject to control by the galR repressor, since they can be further derepressed by growth in the presence of D-fucose. They also synthesize more galactokinase when grown in glycerol as compared to glucose. Thus there are now at least three, and probably four, sites for control of mRNA synthesis in the operator-promoter regions of the gal operon, making it one of the most complex control systems to date for a single operon in bacteria. The complexity is sufficient to accommodate models for differentiation in higher organisms that require more than one "switch" to control a single group of genes.
关键词：lon ; operator ; galactose enzymes ; differentiation