Quantities of ubiquinone bound to proteins in beef heart mitochondria

Ubiquinone-binding proteins were isolated and purified from heavy beef heart mitochondria. 35% of the total ubiquinone in the mitochondria was associated with the purified proteins. About 83% of the associated ubiquinone could be released from the proteins by proteolytic treatment showing that at least 29% (0.87 nmol/mg) of the total ubiquinone (3.0 nmol ubiquinone/mg) in the mitochondria is in the bound form. The purified ubiquinone-binding proteins were resolved into 5 polypeptides with the molecular weights of 17.4, 12.9, 12.6, 9.8 and 8.6 kD on sodium dodecyl sulfate-gel electrophoresis.