title: Thermally induced changes in reconstituted and membranous cytochrome c oxidase.
abstract: The Arrhenius plots of electron transport activity in cytochrome c oxidase reconstituted with well-defined phospholipids have been shown to display a change in slope at 20--25 degrees C regardless of the chemical nature of the incorporated lipid. In native membranous cytochrome c oxidase, the discontinuity in Arrhenius activity plot occurred at 16--18 degrees C. These temperature breaks were found to correlate with changes in spin-label mobilities but not with the bulk lipid transition observed by differential scanning calorimetry. Temperature-dependent reciprocal equilibrium between the immobilized and fluid pools is demonstrated. It is suggested that the changes in kinetic and spin-label spectral characteristics in cytochrome c oxidase membranes are related very likely to a lipid-protein interaction prompted by a thermally induced change in the physical state of the lipids that does not involve a gel to liquid crystalline transition.
mesh_terms: D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006358:Hot Temperature; D008567:Membranes, Artificial; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D003576:Electron Transport Complex IV