The alpha-subunit of the mitochondrial F-1 ATPase interacts directly with the assembly factor Atp12p

The Atp12p protein of Saccharomyces cerevisiae is required for the assembly of the F-1 component of the mitochondrial F1F0 ATP synthase. In this repor t, we show that the F-1 alpha-subunit co-precipitates and copurifies with a tagged form of Atp12p adsorbed to affinity resins, Moreover, sedimentation analysis indicates that in the presence of the F-1 alpha-subunit, Atp12p b ehaves as a particle of higher mass than is observed in the absence of the alpha-subunit. Yeast two-hybrid screens confirm the direct association of A tp12p with the alpha-subunit and indicate that the binding site for the ass embly factor lies in the nucleotide-binding domain of the alpha-subunit, be tween Asp133 and Leu322, These studies provide the basis for a model of F-1 assembly in which Atp12p is released from the alpha-subunit in exchange fo r a beta-subunit to form the interface that contains the non-catalytic aden ine nucleotide-binding site.