The mitochondrial H⁺-ATP synthase synthesizes most of cellular ATP requirements by oxidative phosphorylation (OXPHOS). The ATPase Inhibitory Factor 1 (IF1) is known to inhibit the hydrolase activity of the H⁺-ATP synthase in situations that compromise OXPHOS.

Researchers demonstrate that phosphorylation of S39 in IF1 by mitochondrial protein kinase A abolishes its capacity to bind the H⁺-ATP synthase. Only dephosphorylated IF1 binds and inhibits both the hydrolase and synthase activities of the enzyme.

The phosphorylation status of IF1 regulates the flux of aerobic glycolysis and ATP production through OXPHOS in hypoxia and during the cell cycle. Dephosphorylated IF1 is present in human carcinomas.

Remarkably, mouse heart contains a large fraction of dephosphorylated IF1 that becomes phosphorylated and inactivated upon in vivo β-adrenergic stimulation.

Overall, authors demonstrate the essential function of the phosphorylation of IF1 in regulating energy metabolism.

http://www.cell.com/cell-reports/abstract/S2211-1247(15)00949-3