The complete removal of phospholJpids, including the tightly bound cardiolipin, from Tween 20 solubilized bovine cytochrome bei results in a delipidated enzyme that is reversibly inactivated. The complete removal of the bound phospholipids is achieved by: 1) hydrolyzing the bound phospholipids with snake venom phospholipase A2; and 2) separation of the delipidated enzyme from the resulting lysophospholipids by cytochrome c affinity chromatography. Using these conditions, the detergent solubilized, cardiolipin-free enzyme, retains a native-like structure as indicated by its unperturbed heme environments and a completely oxidized cytochrome c1. However, perturbation of the structure of the cardiolipin free cytochrome bc1 is a function of the method used to reisolate the delipidated enzyme. Use of either MonoQ or DEAE Sephacel chromatography rather than cytochrome c affinity chromatography causes per turbations of the heme centers. Reactivation of cardiolipin free cytochrome bc1 has been achieved at high concentrations of phospholipids. Complete reactivation of the delipidated enzyme is achieved with 5 mM cardiolipin together with 5 mM phosphotidylcholine. Such reactivation does not occur with low concentrations of lipids, e.g. 10 mM phospholipids. Thus, the complete removal of the tightly bound cardiolipin of cytochrome bc1 does not perturb the structure of cytochrome bc1 but the presence of phospholipids is necessary for the enzyme to exhibit ubiquinol:cytochrome c oxidoreductase activity. Supported by NIGMS, GM24795.
|Original language||English (US)|
|State||Published - 1998|
ASJC Scopus subject areas
- Molecular Biology