Mediates the voltage-dependent proton permeability of excitable membranes. Forms a proton-selective channel through which protons may pass in accordance with their electrochemical gradient. Proton efflux, accompanied by membrane depolarization, facilitates acute production of reactive oxygen species in phagocytosis. The dimers display cooperative channel gating (By similarity). The channel activity is inhibited by zinc ions. Homodimer. Detected mainly at intracellular membranes upon overexpression in HeLa cells (PuMed:20147290), but not in other cell types. Enriched in immune tissues, such as lymph nodes, B-lymphocytes, monocytes and spleen. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Unlike other voltage-gated ion channels it lacks the pore domain. The C-terminal coiled coil region mediates homodimerization and cooperative channel gating. It is essential for normal subcellular localization. Phosphorylation may enhance channel gating. Belongs to the hydrogen channel family.