title: Effect of cyanide binding on the copper sites of cytochrome c oxidase: an X-ray absorption spectroscopic study.
abstract: Cu x-ray absorption spectroscopy (XAS) has been used to investigate the effect of cyanide treatment on the structures of the copper sites in beef heart cytochrome c oxidase. The Cu K-edge spectrum changes significantly upon cyanide binding to resting state enzyme, as does the Cu extended x-ray absorption fine structure (EXAFS) spectrum. The Cu EXAFS Fourier transfer (FT) exhibits an enhanced peak for the cyanide-treated enzyme in the region containing the Cu...Fe peak in the resting state FT (at R' approximately equal to 2.6-2.7 A). This peak in the cyanide-treated sample is hypothesized to arise from "outer shell" scattering from a linear Cu-cyanide moiety, suggesting cyanide binding to CuB only (CuB 2+-CN-) or cyanide bridging between the Fe of heme a3 and CuB (Fe3+-(CN-)-CuB 2+).
authors.forename: R A
authors.initials: RA
authors.lastname: Scott
authors.forename: J R
authors.initials: JR
authors.lastname: Schwartz
authors.forename: S P
authors.initials: SP
authors.lastname: Cramer
mesh_terms: D001665:Binding Sites / Q000187:drug effects; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003300:Copper / Q000378:metabolism*; D003486:Cyanides / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D011190:Potassium Cyanide / Q000378:metabolism* / Q000494:pharmacology; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D003486:Cyanides; D003300:Copper; D007501:Iron; D003576:Electron Transport Complex IV; D011190:Potassium Cyanide