title: Reconstitution of the ubiquinol: cytochrome c reductase from a bc1 subcomplex and the 'Rieske' iron-sulfur protein isolated by a new method.
abstract: 1. A method for preparing the 'Rieske' iron-sulfur protein and the bc1 subcomplex of complex III was developed. The new method is advantageous over the published ones in that: (a) the final yield and amount exceeds by far those obtained when employing the hitherto published methods; (b) the iron-sulfur protein as well as the bc1 subcomplex are obtained by one and the same preparation procedure from a common source; and (c) the preparation method is easier than the published ones. 2. The iron-sulfur protein obtained represents the first reconstitutively active preparation present in a monodisperse state. 3. The reconstitution of the ubiquinol:cytochrome c reductase from the two components is a reversible dissociation process. Full activity of ubiquinol:cytochrome c reductase is reached after saturation of the binding site of the bc1 subcomplex for iron-sulfur protein. 4. Full reduction of the constituent cytochrome c1 of the bc1 subcomplex can already be obtained with substoichiometric amounts of iron-sulfur protein, however. 5. The question might be raised whether the observed dissociation equilibrium represents merely a phenomenon occurring specifically with the proteins isolated in Triton X-100 and investigated in a Triton-containing buffer, or whether dissociation of the iron-sulfur protein also takes place in the mitochondrial membrane in the course of the electron-transfer reaction sequence.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003902:Detergents; D014450:Electron Transport Complex III; D007506:Iron-Sulfur Proteins / Q000302:isolation & purification* / Q000502:physiology; D008667:Metalloproteins / Q000302:isolation & purification*; D009097:Multienzyme Complexes / Q000502:physiology; D009247:NADH, NADPH Oxidoreductases / Q000502:physiology; D009994:Osmolar Concentration; D011808:Quinone Reductases / Q000502:physiology
chemical_list: D003902:Detergents; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D009097:Multienzyme Complexes; C037989:Rieske iron-sulfur protein; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III