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Structure of cytochrome a3-Cua3 couple in cytochrome c oxidase as revealed by nitric oxide binding studies

Stevens, Tom H. and Brudvig, Gary W. and Bocian, David F. and Chan, Sunney I. (1979) Structure of cytochrome a3-Cua3 couple in cytochrome c oxidase as revealed by nitric oxide binding studies. Proceedings of the National Academy of Sciences of the United States of America, 76 (7). pp. 3320-3324. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:STEpnas79

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Abstract

The addition of NO to oxidized cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) causes the appearance of a high-spin heme electron paramagnetic resonance (EPR) signal due to cytochrome a3. This suggests that NO coordinates to Cu{a3}+2 and breaks the antiferromagnetic couple by forming a cytochrome a3+3-Cu{a3}+2-NO complex. The intensity of the high-spin cytochrome a3 signal depends on the method of preparation of the enzyme and maximally accounts for 58% of one heme. The effect of N3- on the cytochrome a3+3-Cu{a3}+2-NO complex is to reduce cytochrome a3 to the ferrous state, and this is followed by formation of a new complex that exhibits EPR signals characteristic of a triplet species. On the basis of optical and EPR results, a NO bridge between cytochrome a3+2 and Cu{a3}+2 is proposed-i.e., cytochrome a3+2-NO-Cu{a3}+2. The half-field transition observed at g = 4.34 in the EPR spectrum of this triplet species exhibits resolved copper hyperfine splittings with |A{}| = 0.020 cm-1, indicating that the Cu{a3}+2 in the cytochrome a3+2-NO-Cu{a3}+2 complex is similar to a type 2 copper site.


Item Type:Article
Additional Information:Copyright © 1979 by the National Academy of Sciences. Communicated by Harry B. Gray, April 23, 1979. We thank Dr. Helmut Beinert for critical reviews of this manuscript and several useful discussions on its content. This work was partially supported by Grant GM 22432 from the National Institute of General Medical Sciences, U.S. Public Health Service, and by Grant RR07003 awarded by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health. T.H.S. and G.W.B. are recipients of National Institutes of Health Predoctoral Traineeships. This is contribution no. 5918 from the Division of Chemistry and Chemical Engineering. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.
Subject Keywords:electron paramagnetic resonance; antiferromagnetic coupling; heme proteins; copper proteins; ferroheme-NO
Record Number:CaltechAUTHORS:STEpnas79
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:STEpnas79
Alternative URL:http://www.pnas.org/cgi/content/abstract/76/7/3320
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1498
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:26 Jan 2006
Last Modified:26 Dec 2012 08:44

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