MITOCHONDRIAL ATP SYNTHASE F-1-BETA-SUBUNIT IS A CALCIUM-BINDING PROTEIN

Mitochondrial ATP synthase is responsive to changes in cytosolic calci um concentration, but the regulatory mechanisms are unclear. Here we i dentified a major 52 kDa calcium-binding protein in rat enamel cells a s the mitochondrial ATP synthase F-1-beta-subunit. The F-1-beta-subuni t behaved as a low affinity and moderate capacity calcium-binding prot ein 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 calci um 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.