摘要：SummaryRecently identified proton-activated chloride channel (PAC) contains two transmembrane helices (S1–S2) and is involved in lysosome function, hypoxia adaption, stroke, and carcinogenesis. Although a PAC structure was recently resolved, its gating and activation mechanisms remained largely unknown. By the two-electrode voltage clamp electrophysiology inXenopusoocytes, we found that the hydrophobicity of site 304 at fenestrations, but not that of neighbor sites, is important for maintaining PAC at a closed state at pH 7.5. When activated at acidic pH, PAC activity significantly increased with the hydrophilicity of site 307 within S2, but not with that of neighbor sites, suggesting that 307 acts as an activation gate. We identified six conserved protonatable residues critical for proton-induced activation, consistent with structural studies. Our study depicted a scheme in which proton binding induces conformational changes from the W304-controlled closed state at fenestrations to an activated state controlled by activation gate I307 in helix S2.Graphical abstractDisplay OmittedHighlights•The hydrophobicity of site 304 is critical for maintaining PAC at a closed state•The function of activated PAC is modulated by the hydrophilicity of site 307•Six protonatable amino acids are involved in proton-induced PAC activation•H+binding seem to change PAC from W304-controlled closed to I307-gated open stateMolecular biology; Cell biology; Structural biology
