Figure 5.

Model for the role of Gef1 in the regulation of intravesicular acidic pH and transmembrane voltage. (A and B) Wild-type. (A) Protons H⁺ and copper Cu²⁺ are actively transported into the lumen of post-Golgi vesicles through the Vma1 and Ccc2 ATPases. Anions A⁻ line up at the Gef1 anion channel represented at its closed state. (B) The Gef1 channel opens when a certain voltage is reached in the lumen of the vesicle and allows the entrance of anions that will reduce the membrane potential and facilitate further H⁺ and Cu²⁺ transport. (C and D) gef1 mutant scenario. (C) Same as in A but in the Gef1 anion-channel deficient mutant. (D) The intravesicular voltage will reach high values and no further H⁺ and Cu²⁺ transport will take place.