Conformational substates of bovine heart cytochrome c oxidase: the modified Volpe-Caughey variant.
Kinetic and equilibrium binding studies using optically correlated, quantitative electron paramagnetic resonance (EPR) spectroscopy are reported for the reaction of a modified Volpe-Caughey preparation of bovine heart cytochrome c oxidase with anionic (F-, CN-) and gaseous (NO) ligands. A fast phase of cyanide and fluoride ligation can be attributed to an EPR-silent conformer(s), while the slow and medium phases of cyanide binding are correlated with the g = 12 conformer(s). Using dioxygen or ferricyanide, it is possible to modulate reciprocally the relative amounts of these two species, that together account for at least 95% of the active-site conformers of the resting form of the enzyme.
Young
L J
LJ
Department of Biochemistry, Rice University, Houston, Texas 77251.
D000818:Animals; D002417:Cattle; D003486:Cyanides / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005459:Fluorides / Q000378:metabolism; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation
D003486:Cyanides; D009569:Nitric Oxide; D003576:Electron Transport Complex IV; D005459:Fluorides; D010100:Oxygen