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| Subject Categories: Cellular Metabolism |
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| The EMBO Journal
(2006) 25, 1775–1783, doi:10.1038/sj.emboj.7601064 Published online 6 April 2006 |
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| The effects of mitochondrial iron homeostasis on cofactor specificity of superoxide dismutase 2 |
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| Mei Yang1, Paul A Cobine2, 3, Sabine Molik4, Amornrat Naranuntarat1, Roland Lill4, Dennis R Winge2, 3 and Valeria C Culotta1 |
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1 Division of Toxicological Sciences, Department of Environmental Health Sciences, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA 2 Department of Medicine, University of Utah Health Sciences Center, Salt Lake City, Utah, USA 3 Department of Biochemistry, University of Utah Health Sciences Center, Salt Lake City, Utah, USA 4 Institut fur Zytobiologie, Philipps-Universitat Marburg, Germany To whom correspondence should be addressed Valeria C Culotta, Division of Toxicological Sciences, Department of Environmental Health Sciences, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA. Tel.: +1 410 955 3029; Fax: +1 410 955 0116; E-mail: vculotta@jhsph.edu Received 24 November 2005; Accepted 7 March 2006; Published online 6 April 2006. |
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| Abstract |
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| Many metalloproteins have the capacity to bind diverse metals, but in living cells connect only with their cognate metal cofactor. In eukaryotes, this metal specificity can be achieved through metal-specific metallochaperone proteins. Herein, we describe a mechanism whereby Saccharomyces cerevisiae manganese superoxide dismutase (SOD2) preferentially binds manganese over iron based on the differential bioavailability of these ions within mitochondria. The bulk of mitochondrial iron is normally unavailable to SOD2, but when mitochondrial iron homeostasis is disrupted, for example, by mutations in S. cerevisiae mtm1, ssq1 and grx5, iron accumulates in a reactive form that potently competes with manganese for binding to SOD2, inactivating the enzyme. Studies in mtm1 mutants indicate that iron inactivation of SOD2 involves the Mrs3p/Mrs4p mitochondrial carriers and iron-binding frataxin (Yfh1p). A small pool of SOD2-reactive iron also exists under normal iron homeostasis conditions and binds SOD2 when mitochondrial manganese is low. The ability to control this reactive pool of iron is critical to maintaining SOD2 activity and has important potential implications for oxidative stress in disorders of iron overload. |
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| Keywords: Aft1p, iron, manganese, mitochondria, SOD2 |
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