Question

Explain ATP generation mechanism using proton motive force

Answer 1

ATP is generated from the proton motive force by the enzyme ATP synthase. ATP synthase catalyzes the formation of ATP from ADP and Pi, driven by the flow of protons from the inside of mitochondria to the intermembrane space. It has two functional domains: Fo and F1. The rotational catalysis model explains the mechanism.

Fo is the domain through which protons can pass down their gradient. F1 has three active sites as shown in the hand-drawn diagram attached below to this answer. A given subunit of the F1 begins in the so called -ADP conformation, which has ADP and Pi bound to it from the surrounding medium. The subunit now shifts its conformation to the -ATP conformation which tightly binds ATP. In the third step, the subunit changes to the -empty conformation, which has very low binding affinity towards ATP. The newly synthesized ATP leaves the enzyme surface for the next round of ATP synthesis. This subunit assumes the ADP conformation and the next round begins.

The conformational changes of the F1 domain are driven by the passage of protons through the Fo portion of ATP synthase. The passage of protons rotates the gamma subunit of ATP synthase that brings about these conformational changes.

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