Recombinant sodium channel α subunits expressed in Xenopus oocytes display an anomalously slow rate of inactivation that arises from channels that predominantly exist in a slow gating mode [1,2]. Co-expression of Na− channel β1 subunit with the human skeletal muscle Na+ channel α subunit increases the Na+ current and induces normal gating behavior in Xenopus laevis oocytes. The effects of the β1 subunit can be explained by an allosterically induced conformational switch of the α subunit protein that occurs upon binding the β1 subunit. This binding alters the free energy barriers separating distinct conformational states of the channel. The results illustrate a fundamental modulation of ion channel gating at the molecular level, and specifically demonstrate the importance of the β1 subunit for gating mode changes of Na+ channels.
