Title: Discontinuity between the Voltage-Sensor and the Pore Domain does not Abolish Voltage-Gating of Kv10.1 Potassium Channel
Abstract: Voltage-gating of ion channels is crucial for excitable tissues, such as nerve and muscle. Here we show that a voltage-gated potassium channel retains its voltage-dependency of activation, even when the voltage sensor and the pore domain are expressed as two individual proteins from separate cRNAs in Xenopus laevis oocytes. Not only interrupting the S4-S5 cytoplasmic linker at various positions, but also concomitant deletion of several consecutive amino acids from this region yielded functional channels. Moreover, mutations of the voltage-sensor that shift the conductance-voltage curve in either hyperpolarizing or depolarizing direction cause the same shift when the S4-S5 linker is disrupted. Detailed characterization of how the location of discontinuity affects the voltage and time-dependence of activation and deactivation of the split constructs sheds new light on the coupling between the voltage-sensing module and the channel gate. Our findings indicate that an intact S4-S5 linker is not a sine qua non condition for voltage gating in Kv10.1. In consequence, the idea of direct mechanical coupling between the voltage sensor and the pore mediated by the S4-S5 linker needs to be revised, at least for the KNCH-family channels, which may have a different gating mechanism than Shaker.