Partial resolution of the enzymes catalyzing oxidative phosphorylation. XXIV. A factor required for the binding of mitochondrial adenosine triphosphatase to the inner mitochondrial membrane.

1. Submitochondrial particles have been sequentially treated with trypsin, mea, and sonic oscillation at an alkaline PH. These TUA particles required addition of a protein (F,,) in order to render added ATPase (Fr) sensitive to dicyclohexylcarbodiimide. Further resolution was obtained by exposure of TUA particles either to 2 M sodium thiocyanate or to 1.5% silicotungstate. These procedures removed a second soluble protein component (F,,) which was also required for the sensitivity of ATPase to dicyclohexylcarbodiimide. 2. Preparations of F,, purified from the sodium thiocyanate extract stimulated the 32Pi-ATP exchange reaction and oxidative phosphorylation in silicotungstate-treated submitochondrial particles. 3. Treatment of TUA particles with silicotungstate reduced their ability to bind ATPase (F1). Addition of F,, restored the ability to bind ATPase. It is therefore proposed that F,, is a component which links the mitochondrial ATPase to the inner mitochondrial membrane.