Ion channel proteins form pores in the membranes of cells and are regulated by voltage or small messenger molecules to control information flow to and from cells. The K+ channel, important for the excitability of nerve cells, conducts only K+ ions while completely excluding a smaller ion, Na+. Valiyaveetil et al. show that this selectivity is accomplished in two ways: In the presence of K+, the pore remains open and conductive but collapses when K+ concentrations are low, excluding Na+. In addition, in the conductive state, the pore is lined with multiple binding sites that are specific for K+.
- Choosing Channel Selectivity
A mutant potassium channel stuck in the open position still conducts K+ but not Na+, indicating that its conformation and the presence of K+ in the pore confer selectivity.Permalink: