An S4-S5 Linker Residue Influences Kv2.1 Channel Gating and Inhibition by Carbon Monoxide Releasing Molecule 2 (CORM-2)

Abstract

The carbon releasing molecule 2 (CORM-2) is an allosteric inhibitor of the Shaker and Kv2.1 voltage-gated ion channels. The mechanism of inhibition is common to both channels and derives mainly from an energetic destabilization of the channel's opening transition without inhibiting voltage-sensor activation, thus partially uncoupling voltage-sensor activation from channel gating. Electromechanical coupling between the voltage-sensing domain (VSD) and the pore of Kv channels has been shown to depend on specific interactions between the S4-S5 linker and the carboxyl-terminal portion of the S6 segment. Here, we show that a single glycine to valine mutation in the S4-S5 linker of the Kv2.1 channel causes a large energetic destabilization of the channel's open state. Moreover, the G317V mutation also interferes with the channel's inhibition by CORM-2, suggesting that there is a cavity at the interphase between the VSD and the pore of the channel, including the S4-S5 linker, and that it is part of the CORM-2 binding site in the channel. These data are consistent with the mechanism of channel inhibition by this compound. Supported by Instituto de Ciencia y Tecnologia del Distrito Federal, Grant PIFUTP09-262 to L.D.I.