Spin-State Rationale for the Peroxo-Stabilizing Role of the Thiolate Ligand in Superoxide Reductase

Authors

  • Michael R. Bukowski,

    1. Center for Metals in Biocatalysis and Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA, Fax: (+1) 612-624-7029
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  • Heather L. Halfen,

    1. Deparment of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54702, USA, Fax: (+1) 715-836-4979
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  • Tieme A. van den Berg,

    1. Center for Metals in Biocatalysis and Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA, Fax: (+1) 612-624-7029
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  • Jason A. Halfen Prof. Dr.,

    1. Deparment of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54702, USA, Fax: (+1) 715-836-4979
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  • Lawrence Que Jr. Prof. Dr.

    1. Center for Metals in Biocatalysis and Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA, Fax: (+1) 612-624-7029
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  • This work was supported by grants from the National Science Foundation (CHE-0234951 to J.A.H.) and the National Institutes of Health (GM-33162 to L.Q.). J.A.H. acknowledges sabbatical support from the University of Minnesota NSF/RSEC program (CHE-0113894) and the University of Wisconsin-Eau Claire. The authors would like to acknowledge Dr. Neil R. Brooks, Dr. Victor G. Young, Jr., and the X-Ray Crystallographic Laboratory, Department of Chemistry, University of Minnesota.

Abstract

original image

Anti-push: The axial thiolate ligand stabilizes high-spin FeIII-OOR species (see picture) such as those found in superoxide reductase. This situation is in contrast to the “push effect” observed in structurally similar low-spin FeIII-OOR systems, including cytochrome P450, which promote O[BOND]O bond cleavage. These results show how very similar enzyme-active sites can carry out two very different functions.

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