Which Step Is NOT Part of the Proton-Translocation Process in ATP

Multiple Choice

Which step is NOT part of the proton-translocation process in ATP synthase?

A) A negatively charged amino acid in each c subunit becomes neutral upon proton binding.
B) A positively charged amino acid in the a subunit forms an ion pair with a charged amino acid in a c subunit.
C) Deprotonated c subunits are able to interact only with the a subunit.
D) An arginine in the a subunit is reversibly protonated and deprotonated in each proton binding event.
E) Proton direction is determined by the relative concentrations of protons on either side of the membrane.