title: Interaction of detergents with cytochrome c oxidase.
abstract: The binding of ionic and nonionic, nondenaturing detergents to cytochrome c oxidase has been examined. All bind and displace part but not all of the phospholipid that is associated with the enzyme after isolation. From 6 to 10 phospholipid molecules, depending on the detergent used, do not exchange and these are mostly diphosphatidylglycerol molecules as first shown by Awasthi et al. ((1971) Biochim. Biophys. Acta 226, 42). The binding of Triton X-100 and deoxycholate to the cytochrome c oxidase complex has been studied in detail. Both bind to the enzyme above their critical micelle concentrations: Triton X-100 in the amount of 180 +/- 10 molecules per complex and deoxycholate in the amount of 80 +/- 4 molecules per complex. In nonionic detergents, cytochrome c oxidase exists as a dimer (4 heme complex). The enzyme is dissociated into the monomer or heme aa3 complex by delipidation in bile salts. Activity measurements in different detergents suggest that cytochrome c oxidase requires a flexible, hydrophobic environment for maximal activity and that the dimer or 4 heme complex may be the active species.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide; D002417:Cattle; D002793:Cholic Acids; D003840:Deoxycholic Acid; D003902:Detergents; D003576:Electron Transport Complex IV / Q000378:metabolism; D008823:Micelles; D008931:Mitochondria, Muscle / Q000201:enzymology; D008970:Molecular Weight; D011092:Polyethylene Glycols; D011136:Polysorbates; D011485:Protein Binding
chemical_list: D002793:Cholic Acids; D003902:Detergents; D008823:Micelles; D011136:Polysorbates; D003840:Deoxycholic Acid; D011092:Polyethylene Glycols; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV