Question

How many ATP molecules are synthesized by the F1 subunit of the ATP synthase during a full rotation of the asymmetric gamma subunit?

Group of answer choices

1

12

9

3

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oxidative phosphorylation

Answer 1

3

The F1 part of ATP synthase is made up of 8 subunits, 3α, 3β, γ, δ and ε, where the γ, δ and ε subunits add up to the central stalk (or the rotor shaft) and an alternate arrangement of 3α and 3β form a hexameric ring with a central cavity. The γ subunit inserted in the central cavity protrudes out to meet ε which binds on its side and together they bind the F0.

With every rotation of 120°, γ comes into contact with a different β subunit, and the contact forces that β subunit into the βE conformation. The three subunits switch conformations in such a way that when one holds the βE conformation, one of its flanking subunit assumes the βD form, and the other takes βT form.

As a consequence of a complete rotation of the γ subunit, each β subunit courses through all three possible conformations and three ATP’s are synthesized and delivered by the enzyme.