The Shaker gene of the fruit fly encodes voltage-dependent K+ channel proteins. The long-term goals of the research are to derive a biochemical model for the structure of the channel, and to correlate its functional properties with its structure. The specific aims are: 1) to study the function of the conserved S4 sequence, which has been proposed to be the voltage-sensor of the channel. Single amino acid mutations will be made in the S4 basic amino acids, acidic residues that might form ion pairs with the S4, and control residues. The mutant channels will be expressed in Xenopus oocytes and analyzed electrophysiologically. 2) to study the disposition of the Shaker proteins in the membrane. The modification of potential sites for posttranslational glycosylation will be studied in in vitro translation reactions and in vivo. If these sites are modified in vivo, their topological location can be inferred. 3) to study the subunit structure of the channel. The Shaker gene will be expressed in a tissue culture system to begin biochemical experiments with the eventual goals of purifying the channel and determining the number of Shaker subunits per channel. K+ channels in the nervous system are implicated in the basic mechanisms of epileptogenesis. K+ channels in smooth muscle are promising pharmacological targets for the control of hypertension and stroke. K+ channels in lymphocytes are altered in a mouse model for lupus erythematosus. Therefore, studying the structure and function of K+ channels will contribute to our understanding of the etiology and treatment of a variety of diseases.