Relationship of GxTX-594 labeling to probability of Kv2 voltage sensor activation. (A) EVAP model predictions of concentration and voltage dependence of cell surface fluorescence intensity at different concentrations of EVAP in solution. The bottom axis represents membrane voltage. The left axis represents the predicted fluorescence relative to when all voltage sensors are at rest (Finit) and does not include EVAP signal that is insensitive to voltage. The dashed line corresponds to the right axis and represents the probability that voltage sensors of unlabeled Kv2.1 are in their resting conformation. (B) EVAP model prediction of the cell surface fluorescence when cells are given a +40-mV depolarization relative to when all voltage sensors are at rest (Finit) at increasing concentrations of EVAP. The orange dashed line represents Kd of resting voltage sensors. The blue dashed line represents Kd of activated voltage sensors. (C) EVAP model predictions of concentration and voltage dependence of kΔF. Colors correspond to A, except the dashed line is the probability that voltage sensors bound by GxTX-594 are an activated conformation.
