The Na+/K+-ATPase pumps three sodium ions out of and two potassium ions into the cell while splitting a single molecule of ATP. Here it is found that the carboxy terminus of the ATPase's α-subunit is also a key regulator of a previously unrecognized ion pathway. The data indicate that, in the ATPase's potassium-bound state, a cytoplasmic proton can enter and stabilize site III when empty. When potassium is released, the proton returns to the cytoplasm, thus permitting an overall asymmetric stoichiometry of the transported ions.
- Hanne Poulsen
- Himanshu Khandelia
- Poul Nissen
