X-Ray Absorption Studies of Oriented Cytochrome Oxidase

The polarized X-Ray absorption spectra of the copper and iron sites of cytochrome oxidase in oriented mitochondrial membrane multilayers have been examined. The copper XANES spectra indicate the presence of one tetragonal type copper (Cu8) oriented with the long axis approximately orthogonal to the membrane normal. Quantitative analysis of the copper and iron EXAFS suggests a Cu-S-Fe structure for the binuclear heme a3-CB site.