Affiliation:
1. Department of Biological Sciences, Northern Illinois University, De Kalb, 60115, USA.
Abstract
In Escherichia coli, isochorismate is a common precursor for the biosynthesis of the siderophore enterobactin and menaquinone (vitamin K2). Isochorismate is formed by the shikimate pathway from chorismate by the enzyme isochorismate synthase encoded by the entC gene. Since enterobactin is involved in the aerobic assimilation of iron, and menaquinone is involved in anaerobic electron transport, we investigated the regulation of entC by iron and oxygen. An operon fusion between entC with its associated regulatory region and lacZ+ was constructed and introduced into the chromosome in a single copy. Expression of entC-lacZ was found to be regulated by the concentration of iron both aerobically and anaerobically. An established entC::kan mutant deficient in enterobactin biosynthesis was found to grow normally and synthesize wild-type levels of menaquinone under anaerobic conditions in iron-sufficient media. These results led to the demonstration of an alternate isochorismate synthase specifically involved in menaquinone synthesis encoded by the menF gene. Consistent with these findings, the entC+ strains were found to synthesize enterobactin anaerobically under iron-deficient conditions while the ent mutants failed to do so.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference39 articles.
1. Colorimetric determination of the components of 3,4- dihydroxyphenylalanine-tyrosine mixtures;Arnow L. E.;J. Biol. Chem.,1937
2. Mapping of a mutation affecting regulation of iron uptake systems in Escherichia coli K-12;Bagg A.;J. Bacteriol.,1985
3. The shikimate pathway-a metabolic tree with many branches;Bentley R.;Crit. Rev. Biochem. Mol. Biol.,1990
4. Bentley R. and R. Meganathan. 1987. The biosynthesis of the isoprenoid quinones ubiquinone and menaquinone. In F. C. Neidhardt J. L. Ingraham K. B. Low B. Magasanik M. Schaechter and H. E. Umbarger (ed.) Escherichia coli and Salmonella typhimurium: cellular and molecular biology p. 512-520. American Society for Microbiology Washington D.C.
5. Regulation of divergent transcription from the iron-responsive fepB-entC promoter-operator regions in Escherichia coli;Brickman T. J.;J. Mol. Biol.,1990
Cited by
34 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献