Affiliation:
1. Department of Microbiology, University of Illinois, Urbana 61801.
Abstract
The manganese-containing isozyme of superoxide dismutase (MnSOD) is synthesized by Escherichia coli only during aerobiosis, in accordance with the fact that superoxide can be formed only in aerobic environments. In contrast, E. coli continues to synthesize the iron-containing isozyme (FeSOD) even in the absence of oxygen. A strain devoid of FeSOD exhibited no deficits during either anaerobic or continuously aerobic growth, but its growth lagged for 2 h during the transition from anaerobiosis to aerobiosis. Complementation of this defect with heterologous SODs established that anaerobic SOD synthesis per se is necessary to permit a smooth transition to aerobiosis. The growth deficit was eliminated by supplementation of the medium with branched-chain amino acids, indicating that the growth interruption was due to the established sensitivity of dihydroxyacid dehydratase to endogenous superoxide. Components of the anaerobic respiratory chain rapidly generated superoxide when exposed to oxygen in vitro, suggesting that this transition may be a period of acute oxidative stress. These results show that facultative bacteria must preemptively synthesize SOD during anaerobiosis in preparation for reaeration. The data suggest that evolution has chosen FeSOD for this function because of the relative availability of iron, in comparison to manganese, during anaerobiosis.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference32 articles.
1. Asada K. S. Kanematsu S. Okaka and T. Hayakawa. 1980. Phylogenic distribution of three types of superoxide dismutase in organisms and in cell organelles p. 136-153. In J. V. Bannister and H. A. 0. Hill (ed.) Chemical and biochemical aspects of superoxide and superoxide dismutase. Elsevier/North Holland New York.
2. Molecular mechanism of regulation of siderophore-mediated iron assimilation;Bagg A.;Microbiol. Rev.,1987
3. Superoxide dismutase: improved assays and an assay applicable to acrylamide gels;Beauchamp C.;Anal. Biochem.,1971
4. In vivo competitions between iron and manganese for occupancy of the active site region of the manganese-superoxide dismutase of Escherichia coli;Beyer J.;J. Biol. Chem.,1991
5. Isolation of superoxide dismutase mutants in Escherichia coli: is superoxide dismutase necessary for aerobic life;Carlioz A.;EMBO J.,1986
Cited by
32 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