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Electron Spin Relaxation of Cu_A nd Cytochrome a in Cytochrome c Oxidase. Comparison to heme, copper, and sulfur radical complexes

Brudvig, Gary W. and Blair, David F. and Chan, Sunney I. (1984) Electron Spin Relaxation of Cu_A nd Cytochrome a in Cytochrome c Oxidase. Comparison to heme, copper, and sulfur radical complexes. Journal of Biological Chemistry, 259 (17). pp. 11001-11009. ISSN 0021-9258. http://resolver.caltech.edu/CaltechAUTHORS:20120629-110323859

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Abstract

The method of continuous saturation has been used to measure the electron spin relaxation parameter T_(1)T_(2) at temperatures between 10 and 50 K for a variety of S = 1/2 species including: Cu_A and cytochrome a of cytochrome c oxidase, the type 1 copper in several blue copper proteins, the type 2 copper in laccase, inorganic Cu(II) complexes, sulfur radicals, and low spin heme proteins. The temperature dependence and the magnitude of T_(1)T_(2) for all of the species examined are accounted for by assuming that the Van Vleck Raman process dominates the electron spin-lattice relaxation. Over the entire temperature range examined, the relaxation of the type 1 coppers in six to seven times faster than that of type 2 copper, inorganic copper, and sulfur radicals, in spite of the similar g-anisotropies of these species. This result may indicate that the coupling of the phonon bath to the spin center is more effective in type 1 coppers than in the other complexes studied. The relaxation of Cu_A of cytochrome oxidase exhibits an unusual temperature dependence relative to the other copper complexes studied, suggesting that the protein environment of this center is different from that of the other copper centers studied and/or that Cu_A is influenced by a magnetic dipolar interaction with another, faster-relaxing paramagnetic site in the enzyme. A comparison of the saturation characteristics of the Cu_A EPR signal in native and partially reduced CO complexes of the enzyme also suggests the existence of such an interaction. The implications of these results with respect to the disposition of the metal centers in cytochrome oxidase are discussed


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http://www.jbc.org/content/259/17/11001.abstractPublisherUNSPECIFIED
Additional Information:© 1984 American Society for Biochemistry and Molecular Biology. Received for publication, April 3, 1984. Recipient of National Research Service Award 5T32GM-07616 from the National Institute of General Medical Sciences. Recipient of National Research Service Award 5T32GM-07616 from the National Institute of General Medical Science. Recipient of Grant GM-22432 from the National Institute of General Medical Sciences and Biomedical Research Support Grant RR 07003. We are grateful to Craig T. Martin, Jeff Gelles, and Joel Morgan for technical assistance and helpful discussions. This paper is Contribution 6823 from the Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Funders:
Funding AgencyGrant Number
National Institute of General Medical Science National Research Service Award5T32GM-07616
National Institute of General Medical SciencesRR 07003
National Institute of General Medical SciencesGM-22432
Record Number:CaltechAUTHORS:20120629-110323859
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120629-110323859
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ID Code:32199
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:02 Jul 2012 15:31
Last Modified:02 Jul 2012 15:31

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