Mitochondrial ATP synthase F-1-beta-subunit is a calcium-binding protein

Mitochondrial ATP synthase is responsive to changes in cytosolic calcium concentration, but the regulatory mechanisms are unclear. Here we identified a major 52 kDa calcium-binding protein in rat enamel cells as the mitochondrial ATP synthase F-1-beta-subunit. The F-1-beta-subunit behaved as a low affinity and moderate capacity calcium-binding protein during comparative Ca-45 overlay analyses, Equivalent behavior was shown by the F-1-beta-subunit from rat liver mitochondria, but not by the homologous F-1-alpha-subunit, supporting the specificity of calcium binding. Evidence that the catalytic F-1-beta-subunit binds calcium specifically introduces new mechanistic possibilities for regulating ATP synthase, and thereby coordinating ATP production with demand for ATP-fuelled calcium pump activity.