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 i