Question

Which of the following statements accurately represent the basic principles of the binding change mechanism concerning ATP synthase? Choose one or more:

A. The y subunit directly contacts all three β-subunits; however, each of these interactions is distinct, giving rise to three different B-subunit conformations.

B. The ATP binding affinities of the three β-subunit conformations are defined as L (loose), T (tight), and O (open). ADP and Pi bind to the L conformation, whereas ATP binds tightly to the T conformation. ATP is released from the enzyme when the B subunit is in the O conformation.

C. As protons flow through Fo, the y subunit rotates counterclockwise during ATP synthesis (looking at F1 from the matrix side), such that with each 120° rotation, the B subunits sequentially undergo conformational changes from L to T to O to L.

D. One full rotation of the y subunit should generate nine ATP, as each B subunit will have cycled once through the T state. Moreover, the β-subunit conformations should be independent, so that when one subunit is in the T conformation, the other two subunits can be in any O and/or L conformations.

Answer 1

Correct statements on the basic principles of the binding change mechanism of ATP synthase include the distinct interactions of the γ subunit with β-subunits, ATP binding affinities represented by L, T, and O conformations, and the production of three ATP molecules per full rotation of the γ subunit.

Step-by-step explanation:

The basic principles of the binding change mechanism concerning ATP synthase which accurately represent the process include:

• A. The γ subunit directly contacts all three β-subunits; however, each of these interactions is distinct, giving rise to three different β-subunit conformations.
• B. The ATP binding affinities of the three β-subunit conformations are L (loose), T (tight), and O (open). ADP and Pi bind to the L conformation, ATP binds tightly to the T conformation, and ATP is released from the enzyme when the β subunit is in the O conformation.
• C. As protons flow through Fo, the γ subunit rotates, facilitating a sequential conformational change in the β subunits from L to T to O to L with each 120° rotation.

Statement D is incorrect because one full rotation of the γ subunit generates three ATP molecules, not nine. For each 360° rotation, each β subunit cycles through L, T, and O states once, thereby coordinating the conformational states of all β subunits at a given time.