ATP-synthese: mechanisme

ATP synthase is a molecular machine where the movement of protons drives the rotation of the central stalk or the γ-subunit.

This rotating γ-subunit passes through a hexameric-globular head made of three α-β subunit pairs.

Each β subunit has a catalytic site that can attain three conformational states: open, loose, and tight, each varying in its affinity for the substrates and the product.

The catalytic cycle for ATP synthesis begins with the open-state of a β subunit. The substrates- ADP and inorganic phosphate can then enter the catalytic site.

When the γ-subunit rotates 120 degrees, it transforms the catalytic site into a loose-state. This allows substrates to weakly bind to the catalytic site.

As the γ-subunit rotates another 120 degrees, the catalytic site switches to the tight-state. This causes the substrates to tightly bind to the catalytic site and spontaneously condense into a tightly-bound ATP.

In the next γ-subunit rotation, the catalytic-site switches back to the open-state, where it loses the affinity for ATP, thereby releasing it.

Overall, the process continues with the proton-induced spinning of the rotor and the central stalk, followed by the conformation changes in the globular head that enable the entry of ADP and inorganic phosphate and subsequent generation of ATP.