F0F1ATPsyntas

F0F1 ATP synthase is a membrane-bound enzyme complex that synthesizes ATP, the cell’s main energy currency, by using the proton motive force generated by electron transport chains in mitochondria, chloroplasts, and many bacteria. It can also operate in reverse, hydrolyzing ATP to pump protons under certain conditions.

The enzyme consists of two linked sectors: Fo, embedded in the membrane, and F1, protruding into the cytoplasm or mitochondrial matrix. Fo forms the proton channel and includes a subunit a and a ring of c subunits that rotate within the membrane. F1 contains the catalytic core, composed of three pairs of α and β subunits forming a hexamer, plus the central stalk made of γ and ε subunits and the surrounding δ subunit. The flow of protons through Fo drives rotation of the c-ring and the connected γ subunit, which in turn induces conformational changes in the β-subunits to catalyze ATP synthesis from ADP and inorganic phosphate.

The mechanism is often described as rotational catalysis and the binding-change model. As the central shaft turns, each β-subunit cycles through three conformations, facilitating substrate binding, chemical reaction, and product release. The overall efficiency and the exact ATP yield per proton depend on the c-ring stoichiometry, which varies among organisms and organelles.

Regulation and inhibition are well characterized. Certain antibiotics and inhibitors, such as oligomycin, block Fo function, preventing proton flow. The enzyme is reversible, so ATP hydrolysis can be used to maintain the proton gradient when respiration is limited.

F0F1 ATP synthase is essential for energy metabolism, linking electron transport to ATP production and supporting cellular processes across diverse life forms.