A voltage-sensor water pore.

Voltage-sensor (VS) domains cause the pore of voltage-gated ion channels to open and close in response to changes in transmembrane potential. Recent experimental studies suggest that VS domains are independent structural units. This independence is revealed dramatically by a voltage-dependent proton-selective channel (Hv), which has a sequence homologous to the VS domains of voltage-gated potassium channels (Kv). Here we show by means of molecular dynamics simulations that the isolated open-state VS domain of the KvAP channel in a lipid membrane has a configuration consistent with a water channel, which we propose as a common feature underlying the conductance of protons, and perhaps other cations, through VS domains.