Structure of cytochrome oxidase redox center in native and modified forms.

X-ray synchrotron studies gives the dimensions of the iron- sulfur-copper (Fe-S-Cu) binuclear active site of cytochrome oxidase and reports the extension of structural studies to forms that further support the previously determined structures by (a) removal of copper and (b) the rupture of the S-bridge in the oxidized form. Both these chemical modifications give appropriate changes in the EXAFS signals that are consistent with the Fe-S-Cu configuration. These studies afford a structural basis for oxidase, peroxidase, and catalase activities of cytochrome oxidase and suggest mechanisms of charge separation and energy conservation.