title: Integral polypeptide composition of Complex III of the mitochondrial electron-transfer chain.
abstract: Phospholipids in isolated Complex III of the mitochondrial electron-transfer chain were depleted by hydrophobic chromatography. The complex was further purified by affinity chromatography. The polypeptide composition of the complex was examined using SDS-polyacrylamide gel electrophoresis. Ten polypeptides were demonstrated in the gel pattern of the complex containing more than 10% (w/w) phospholipids; and 9 polypeptides, in the pattern of the complex containing 5% phospholipids. Although the enzymic activity of the complex composed of the 9 polypeptides was about a half of that of the original enzyme, it was fully restored when soybean phospholipid mixture was added. Further depletion of phospholipids to 0.6% makes the iron-sulfur protein dissociable from the complex, resulting in a loss of the enzymic activity (Shimomura, Y. and Ozawa, T. (1982) Biochem. Int. 5, 1-6). These results suggest that Complex III consists of 9 polypeptides, and the smallest polypeptide is a contaminant embedded in phospholipids with respect to the electron-transfer capability of the complex.
mesh_terms: D000818:Animals; D002417:Cattle; D003573:Cytochrome b Group / Q000032:analysis*; D003574:Cytochrome c Group / Q000031:analogs & derivatives*; D003575:Cytochromes c1 / Q000032:analysis*; D004579:Electron Transport; D014450:Electron Transport Complex III; D004591:Electrophoresis, Polyacrylamide Gel; D008563:Membrane Lipids / Q000502:physiology; D008929:Mitochondria, Heart / Q000201:enzymology*; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000302:isolation & purification* / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification*; D010743:Phospholipids / Q000494:pharmacology*; D011808:Quinone Reductases / Q000302:isolation & purification* / Q000378:metabolism; D014451:Ubiquinone / Q000032:analysis
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D008563:Membrane Lipids; D009097:Multienzyme Complexes; D010743:Phospholipids; D014451:Ubiquinone; D003575:Cytochromes c1; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III