XAS Studies on the CuA Centers of Heme-Copper Oxidases and Loop-Directed Mutants of Azurin: Implications for Redox Reactivity
- N. J. BlackburnN. J. BlackburnDepartment of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, P.O. Box 91000, Portland, OR 97291-1000More by N. J. Blackburn
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- M. RalleM. RalleDepartment of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, P.O. Box 91000, Portland, OR 97291-1000More by M. Ralle
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- D. SandersD. SandersDepartment of Biology, University of California at San Diego, La Jolla, CA 92093More by D. Sanders
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- J. A. FeeJ. A. FeeDepartment of Biology, University of California at San Diego, La Jolla, CA 92093More by J. A. Fee
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- S. de VriesS. de VriesDepartment of Microbiology and Enzymology, Technical University of Delft, 2628 BC Delft, NetherlandsMore by S. de Vries
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- R. P. HouserR. P. HouserDepartment of Chemistry and Center for Metal in Biocatalysis, University of Minnesota, Minneapolis, MN 55455More by R. P. Houser
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- W. B. TolmanW. B. TolmanDepartment of Chemistry and Center for Metal in Biocatalysis, University of Minnesota, Minneapolis, MN 55455More by W. B. Tolman
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- M. T. HayM. T. HayDepartment of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801More by M. T. Hay
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- Y. LuY. LuDepartment of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801More by Y. Lu
Abstract
The heme-copper oxidases (historically termed cytochrome oxidases) are ubiquitous in both prokaryotic and eukaryotic aerobic organisms. They function to catalyze the 4-proton, 4-electron reduction of dioxygen to water and transduce the energy made available from O-O bond cleavage to the translocation of an additional 4 protons across the cytoplasmic or mitochondrial membrane. The energy released is stored as an electrochemical gradient and utilized to drive ATP synthesis in the process known as oxidative phosphorylation. For these reasons, heme-copper oxidases are arguably the most important enzymes in mammalian cells, providing the energy for most metabolic processes and consuming 80-90% of the oxygen we breathe.
The catalytic activity of the heme copper oxidases resides in subunit I which is a membrane-spanning polypeptide, containing a dinuclear high-spin heme-CuB dioxygen binding site and a low-spin heme center. A second subunit (II) contains the binding site for the electron donor. A number of differing classes