Molecular basis of multistep voltage activation in plant two-pore channel 1

Significance Despite decades of biophysical and structural research, little is understood about how voltage-gated ion channels (VGICs) activate during membrane depolarization, and less is known about how VGICs can be modulated by lipids and other ligands. We identify multiple functional states of the voltage- and Ca 2+ -gated ion channel TPC1 from Arabidopsis thaliana (AtTPC1), which confers electrical excitability to the plant vacuole. Here, we show how a voltage-sensing domain (VSD) functions during electrical activation and the mechanism of inhibition by vacuolar Ca 2+ . We show that the VSD undergoes large-scale, domain-wide structural changes during activation that involves Ca 2+ -dependent in-membrane plane rotation, subsequent charge transfer, and a Ca 2+ -dependent gate in the pore mouth that is allosterically coupled to the VSD.