title: An ubiquinone-binding protein in mitochondrial NADH-ubiquinone reductase (Complex I).
abstract: An ubiquinone-binding protein (QP) was purified from mitochondrial NADH-ubiquinone reductase (Complex I). Complex I was separated into 3 fragments: a fraction of hydrophobic proteins, that of soluble iron-sulfur protein (IP) and soluble NADH dehydrogenase of flavoprotein by a procedure involving the resolution with DOC and cholate, followed by ethanol and ammonium acetate fractionations. About 40% of the total ubiquinone was recovered in the IP fragment which consisted of 12 polypeptides. The QP was purified from the IP fragment with a hydrophobic affinity chromatography. SDS-polyacrylamide gel electrophoresis showed that the purified QP corresponded to 14-kDa polypeptide of the IP fragment and was a different protein from the QP (12.4 kDa) in Complex III. The purified QP (14 kDa) contained one mol ubiquinone per mol. The ubiquinone-depleted IP fragment could rebind ubiquinone. These results indicate that an ubiquinone-binding site in Complex I is on the 14-kDa polypeptide of the IP fragment.
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002417:Cattle; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases / Q000032:analysis* / Q000378:metabolism; D013367:Submitochondrial Particles / Q000032:analysis*; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D007506:Iron-Sulfur Proteins; C027208:ubiquinone-binding proteins; D014451:Ubiquinone; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases