BPS2026 – Structure, function, and dynamics of alkaline gating in a pentameric ion channel

Pentameric ligand-gated ion channels (pLGICs) are crucial for electrochemical signal transduction across evolution. As with many signaling proteins, their function is influenced by environmental factors including pH and small molecules; however, their underlying mechanisms of allosteric gating remain unclear. The prokaryotic channel sTeLIC offers a valuable model system for such processes, as it is activated at alkaline pH, and sensitive to modulation by aromatic compounds via the extracellular vestibule. Here, we determined cryo-EM structures in resting and activating conditions, subjected them to constant-pH molecular dynamics simulations, and assessed targeted mutations through oocyte electrophysiology. Our results substantiate a mechanism for pH sensing and pore gating involving rearrangement of glutamate residues located in the domain-interface and extracellular-vestibule regions of each subunit. This work provides a detailed structure-function mechanism for allosteric activation by alkalinization, with potential parallels in pH and ion sensitivity among eukaryotic pLGICs.