Question

Describe (in detail) the molecular mechanism of how ATP Synthase rotates and produces ATP. Know the role of the “C” protein, the shaft protein, and the alpha-beta dimers.

Answer 1

c-subunit acts as rotor unit of ATP synthase. the proton enters through this channel.

Movement of 3 protons from IMS back to matrix leads to the conformational change in 3 beta subunits which is responsible for binding of ADP + inorganic phosphate, synthesis of ATP and release of ATP from three different subunits.

Hence, total 9 protons are needed for completing one cycle of ATP synthesis and release.

But the same 9 H+ also synthesizes 2 other ATPs in different subunits. Hence, it leads to the synthesis of 3 ATPs.

Therefore, on an average, 3 H+ are required for synthesis of 1 ATP. One more H+ is needed to maintain high phosphate concentration or phosphate transport in the mitochondrial matrix. Hence, together, we can say that 4 H+ are needed to synthesize 1 ATP.

NADH pumps 10 H+ from matrix to IMS. These H+ come back into matrix and leads to the synthesis of 2.5 ATPs (10/4).

Similarly, FADH2 or succinate is responsible for 6 H+ movement from matrix to IMS. When they come back into matrix, they synthesize 1.5 ATP (6/4)