8ijn
Bovine Heart Cytochrome c Oxidase in the Nitric Oxide-Bound Fully Reduced State at 100 K
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. Publication Abstract from PubMedThe O(2) reduction site of cytochrome c oxidase (CcO), comprising iron (Fe(a3)) and copper (Cu(B)) ions, is probed by x-ray structural analyses of CO, NO, and CN(-) derivatives to investigate the mechanism of the complete reduction of O(2). Formation of the derivative contributes to the trigonal planar coordination of and displaces one of its three coordinated imidazole groups while a water molecule becomes hydrogen bonded to both the CN(-) ligand and the hydroxyl group of Tyr244. When O(2) is bound to , it is negatively polarized ( ), and expected to induce the same structural change induced by CN(-). This structural change allows to receive three electron equivalents nonsequentially from , , and Tyr-OH, providing complete reduction of O(2) with minimization of production of active oxygen species. The proton-pumping pathway of bovine CcO comprises a hydrogen-bond network and a water channel which extend to the positive and negative side surfaces, respectively. Protons transferred through the water channel are pumped through the hydrogen-bond network electrostatically with positive charge created at the Fe(a) center by electron donation to the O(2) reduction site. Binding of CO or NO to induces significant narrowing of a section of the water channel near the hydrogen-bond network junction, which prevents access of water molecules to the network. In a similar manner, O(2) binding to is expected to prevent access of water molecules to the hydrogen-bond network. This blocks proton back-leak from the network and provides an efficient gate for proton-pumping. Bovine cytochrome c oxidase structures enable O2 reduction with minimization of reactive oxygens and provide a proton-pumping gate.,Muramoto K, Ohta K, Shinzawa-Itoh K, Kanda K, Taniguchi M, Nabekura H, Yamashita E, Tsukihara T, Yoshikawa S Proc Natl Acad Sci U S A. 2010 Apr 12. PMID:20385840[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References | ||||||||||||||||||||
