Three-Dimensional Structure of the S4–S5 Segment of the Shaker Potassium Channel

Abstract

The propagation of action potentials during neuronal signal transduction in phospholipid membranes is mediated by ion channels, a diverse group of membrane proteins. The S4–S5 linker peptide (S4–S5), that connects the S4 and S5 transmembrane segments of voltage-gated potassium channels is an important region of the Shaker ion-channel protein. Despite its importance, very little is known about its structure. Here we provide evidence for an amphipathic α-helical conformation of a synthetic S4–S5 peptide of the voltage-gated Drosophila melanogaster Shaker potassium channel in water/trifluoroethanol and in aqueous phospholipid micelles. The three-dimensional solution structures of the S4–S5 peptide were obtained by high-resolution nuclear magnetic resonance spectroscopy and distance-geometry/simulated-annealing calculations. The detailed structural features are discussed with respect to model studies and available mutagenesis data on the mechanism and selectivity of the potassium channel.