Figure 5.

Model for cytoplasmic domain regulation of pH gating. Two of four subunits are shown. At pH 7, the cytoplasmic domains and the cluster region formed by the charged amino acids at the boundary between the membrane and cytoplasm are neutral, resulting in an oligomer that stabilizes the closed state. At pH 4, the cytoplasmic domains and the cluster region are positively charged. This causes them to repel one another, resulting in a rearrangement that opens the pore.