Scientists identified a mutation in a mitochondrial gene encoding a component of ATP synthase. People who have this mutation suffer from muscle weakness, ataxia, and retinitis pigmentosa. Scientists performed a tissue biopsy on three patients with this mutation, and they isolated submitochondrial particles capable of succinate‑sustained ATP synthesis. First, the scientists measured the amount of ATP synthesized by ATP synthase after the addition of succinate. The results they obtained are shown in the table.

Sample nmol of ATP formed min–1 mg–1
Control 3.0
Patient 1 0.25
Patient 2 0.11
Patient 3 0.17
Why did the scientists add succinate to the submitochondrial particles?

Oxidation of succinate generates electrons that are used to establish a proton‑motive force that powers ATP synthesis.

ATP synthase reduces succinate to provide energy for ATP synthesis.

ATP synthase oxidizes succinate to provide energy for ATP synthesis.

Reduction of succinate through the electron transport chain establishes a proton‑motive force that powers ATP synthesis.
What is the effect of the mutation on succinate‑coupled ATP synthesis?

The mutation had no effect on ATP synthesis in all three patients.

The mutation did not affect ATP synthesis in patients 1 and 3, but greatly reduced ATP synthesis in patient 2.

The mutation reduced ATP synthesis in all three patients.

The mutation did not affect ATP synthesis in patient 1, but greatly reduced ATP synthesis in patients 2 and 3.
Next, scientists measured the ATPase activity of ATP synthase by incubating the submitochondrial particles with ATP. Since succinate inhibits ATP hydrolysis, the scientists carried out this experiment in the absence of succinate. The results obtained are shown in the table.

Sample nmol of ATP hydrolyzed min–1 mg–1
Control 33
Patient 1 30
Patient 2 25
Patient 3 31
What is the effect of the mutation on ATP hydrolysis?

The mutation drastically decreased the ATP hydrolysis activity of patient 1 and 2, but did not affect the ATP hydrolysis activity of patient 3.

The mutation drastically decreased the ATP hydrolysis activity of ATP synthase in all three patients.

The mutation increased the ATP hydrolysis activity of ATP synthase.

The mutation did not affect the ATP hydrolysis activity of ATP synthase in any of the three patients.
What do these results suggest about the nature of the mutation in ATP synthase?

The mutation prevented ATP synthase from binding to ATP.

The mutation did not affect the catalytic site of the ATP synthase in all three patients.

The mutation prevented ATP synthase from binding to succinate.

The mutation decreased the amount of ATP synthase present in all three patients.