3abm
Bovine heart cytochrome c oxidase at the fully oxidized state (200-s X-ray exposure dataset)
Structural highlights
FunctionCOX1_BOVIN Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Subunits 1-3 form the functional core of the enzyme complex. CO I is the catalytic subunit of the enzyme. Electrons originating in cytochrome c are transferred via the copper A center of subunit 2 and heme A of subunit 1 to the bimetallic center formed by heme A3 and copper B. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe fully oxidized form of cytochrome c oxidase, immediately after complete oxidation of the fully reduced form, pumps protons upon each of the initial 2 single-electron reduction steps, whereas protons are not pumped during single-electron reduction of the fully oxidized "as-isolated" form (the fully oxidized form without any reduction/oxidation treatment) [Bloch D, et al. (2004) The catalytic cycle of cytochrome c oxidase is not the sum of its two halves. Proc Natl Acad Sci USA 101:529-533]. For identification of structural differences causing the remarkable functional difference between these 2 distinct fully oxidized forms, the X-ray structure of the fully oxidized as-isolated bovine heart cytochrome c oxidase was determined at 1.95-A resolution by limiting the X-ray dose for each shot and by using many (approximately 400) single crystals. This minimizes the effects of hydrated electrons induced by the X-ray irradiation. The X-ray structure showed a peroxide group bridging the 2 metal sites in the O(2) reduction site (Fe(3+)-O(-)-O(-)-Cu(2+)), in contrast to a ferric hydroxide (Fe(3+)-OH(-)) in the fully oxidized form immediately after complete oxidation from the fully reduced form, as has been revealed by resonance Raman analyses. The peroxide-bridged structure is consistent with the reductive titration results showing that 6 electron equivalents are required for complete reduction of the fully oxidized as-isolated form. The structural difference between the 2 fully oxidized forms suggests that the bound peroxide in the O(2) reduction site suppresses the proton pumping function. A peroxide bridge between Fe and Cu ions in the O2 reduction site of fully oxidized cytochrome c oxidase could suppress the proton pump.,Aoyama H, Muramoto K, Shinzawa-Itoh K, Hirata K, Yamashita E, Tsukihara T, Ogura T, Yoshikawa S Proc Natl Acad Sci U S A. 2009 Feb 17;106(7):2165-9. Epub 2009 Jan 21. PMID:19164527[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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