14-3-3 protein is a regulator of the mitochondrial and chloroplast ATP synthase

Abstract

Mitochondrial and chloroplast ATP synthases are key enzymes in plant metabolism, providing cells with ATP, the universal energy currency. ATP synthases use a transmembrane electrochemical proton gradient to drive synthesis of ATP. The enzyme complexes function as miniature rotary engines, ensuring energy coupling with very high efficiency. Although our understanding of the structure and functioning of the synthase has made enormous progress in recent years, our understanding of regulatory mechanisms is still rather preliminary. Here we report a role for 14-3-3 proteins in the regulation of ATP synthases. These 14-3-3 proteins are highly conserved phosphoserine͞phosphothreonine-binding proteins that regulate a wide range of enzymes in plants, animals, and yeast. Recently, the presence of 14-3-3 proteins in chloroplasts was illustrated, and we show here that plant mitochondria harbor 14-3-3s within the inner mitochondrial-membrane compartment. There, the 14-3-3 proteins were found to be associated with the ATP synthases, in a phosphorylation-dependent manner, through direct interaction with the F 1 ␤-subunit. The activity of the ATP synthases in both organelles is drastically reduced by recombinant 14-3-3. The rapid reduction in chloroplast ATPase activity during dark adaptation was prevented by a phosphopeptide containing the 14-3-3 interaction motif, demonstrating a role for endogenous 14-3-3 in the down-regulation of the CF oF1 activity. We conclude that regulation of the ATP synthases by 14-3-3 represents a mechanism for plant adaptation to environmental changes such as light͞dark transitions, anoxia in roots, and fluctuations in nutrient supply.

Human ATP synthase beta is phosphorylated at multiple sites and shows abnormal phosphorylation at specific sites in insulin-resistant muscle

“…In rat renal cells, PRKCAmediated serine phosphorylation of ATPsyn-β was associated with a decreased ATP synthase activity in vitro [30]. Moreover, in plant mitochondria, the binding of recombinant 14-3-3 protein to phosphorylated serine/threonineresidues on ATPsyn-β inhibited ATP synthase activity [36]. Of interest, Thr213 is located within the nucleotide-binding region, indicating that phosphorylation at this site may interfere with the binding of ADP and Pi to the catalytic sites on ATPsyn-β, and therefore could interfere with ATP synthesis.…”

Proteome Analysis Reveals Phosphorylation of ATP Synthase β-Subunit in Human Skeletal Muscle and Proteins with Potential Roles in Type 2 Diabetes

“…Because there is no report to date on the phosphorylation of human ATPsyn␤ it is uncertain how such post-translational modification interacts with the proposed binding-change model for ATP synthesis, in which conformational changes in the nucleotide-binding sites of the three ␤-subunits are coupled to the catalytic activity of F 1 -ATP synthase (27). That phosphorylation of human ATPsyn␤ may play a role for the catalytic activity of F 1 -ATP synthase is suggested by the recent observation that phosphoserine/phosphothreonine-binding 14 -3-3 proteins were found to be associated with mitochondrial ATP synthase in plants in a phosphorylation-dependent manner through direct interaction with the ␤-subunit of F 1 -ATP synthase and that the activity of ATP synthase was reduced by recombinant 14 -3-3 protein (28). Consistent with the reduced expression of ATPsyn␤ in our study, several other studies argue for a lower ATP synthase activity in diabetic muscle.…”

14-3-3 Proteins Are Constituents of the Insoluble Glycoprotein Framework of the Chlamydomonas Cell Wall

“…(Oecking et al, 1994;Baunsgaard et al, 1998;Fullone et al, 1998). Furthermore, 14-3-3 proteins occur in chloroplasts and plant mitochondria, where they regulate ATP synthase activities (Bunney et al, 2001;Aducci et al, 2002;Jarvis and Soll, 2002;Soll, 2002). Although 14-3-3 proteins have been found in several organelles, their presence in the extracellular matrix has not been described.…”