Mitochondrial ATP synthase F1‐β‐subunit is a calcium‐binding protein

Abstract

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 F₁-β-subunit. The F₁-β-subunit behaved as a low affinity and moderate capacity calcium-binding protein during comparative ⁴⁵Ca overlay analyses. Equivalent behavior was shown by the F₁-β-subunit from rat liver mitochondria, but not by the homologous F₁-α-subunit, supporting the specificity of calcium binding. Evidence that the catalytic F₁-β-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.