FIGURE 9.

Model for cation accumulation in the vacuole. Vacuolar membrane-bound antiporters Vcx1p and Vnx1p use the proton gradient generated by the V-ATPase to energize the transport of cations into the lumen of the main vacuole. The contribution of the pre-vacuolar alkali cation/H⁺ antiporter, Nhx1p, in the accumulation of K⁺ and Na⁺ remains to be determined. Nhx1p could play a role in the loading of the PVC from which vesicles containing ions are sent to the main vacuoles and therefore contribute to the accumulation of ions in the vacuolar lumen. Knowing the importance of Nhx1p in the control of the vesicular trafficking, this antiporter could play a role in the targeting of uncharacterized cation transporters (?) to the vacuolar membrane and indirectly affect ion homeostasis of the vacuole.