Question

You can create a vesicle from the inner mitochondrial membrane that includes a functional ATP synthase protein with its fully functional F0 rotor, central stalk, and F1 ATPase head. There is ATP, ADP, and Pi (inorganic phosphate) present inside and outside of the vesicle. You are allowed to mechanically spin the F0 rotor domain in the absence of protons. How would ATP levels change inside the vesicle? Briefly explain how this change occurs.

Answer 1

Most of the ATP synthesized in glucose metabolism is produced in mitochondria by oxidative phosphorylation. The ATP synthase is made up of F0 region which is mitochondrial inner membrane bound and F1 region which is exposed to matrix. These two regions are linked by two stalks, the F1 central stalk and the F0 peripheral stalk. ATP6, together with the c-ring forms the proton-conducting channel of the F0 region. Transport of protons across the F0 rotor module results in rotation of c-ring. The torque of the c-ring is transmitted to the catalytic head of F1 region via the gamma-subunit of the central stalk. The respiratory chain complexes pump protons across the inner membrane into intermembrane space thereby generating proton motive force. This force drives the ATP synthase to synthesize ATP. ATP synthase couples the synthesis of ATP to the transport of protons into the matrix. So when the F0 rotor domain is spinned in absence of protons, there will be no ATP synthesis as there will be no proton motive force to drive the reaction.