Analysis and design of ion channel proteins

Two important features associated with ion channel proteins antheir ion .selectivity and rectification De novo design provides an attractive approach ID probe the minimal features required for these functions. We have prepared two simple models tor ion channel proteins using alpha-helical peptides composed of only Leu and Ser residues. These peptides are believed to form helical bundles with a central pore- that conducts ions across membranes. Derivatives have been prepared to determine how electrostatic and steric interactions affect ion selectivity and rectification The principals these studies have also been applied tu the analysis ol a proton-selective channel protein iM2) t rum the m!iuen/a A virus M2 contains a single transmembrane helix domain, which forms tetramers m membranes. Based on a combination ot site directed mutagenesis. computer modeling, and spectroscopic studies, the structure ol this t ran s mem bra ne helical bundle has been structurally characten/ed. Cysteine-scanning was used to generate a series ot mutants with successive substitutions m the transmembrane segment ot the protein, and the effects on reversal potential, ion currents and amantadmr resistance were measured. Fourier analysis revealed a periodicity consistent with a 4stranded coiled coil or helical bundle. A three-dimensional model of (ins structure suggests a possible mechanism lor the proton selectivity of the M-" channel of influenJ.a virus.