The overall objectives of this research program since its inception have been to develop nuclear magnetic resonance (NMR) techniques and use them in concert with other experimental approaches to elucidate the molecular structure and physiologic functions of selected membrane-targeting proteins involved in vision and other signal transduction processes. During the next five years, we will use NMR, fluorescence, microcalorimetry, x-ray crystallography and high-throughput functional analysis to delineate the structure, functions and mechanism of action of a family of calcium-myristoyl switch proteins that serve as membrane targeting regulators in signaling and are linked to retinal and neurological diseases. In particular, retinal recoverin has been implicated in cancer associated retinopathy, an autoimmune disease in the retina caused by a primary tumor in another tissue. Also, point mutations in the guanylate cycalse activating proteins (GCAPs) are genetically linked to autosomal dominant cone dystrophy. By continuing our intensive study of retinal recoverin and the GCAP proteins and by broadening its scope to encompass homologs and targets, we hope to gain a deeper understanding of how calcium-myristoyl switches operate in membrane signaling and retinal disease. In particular, we want to understand how covalently attached myristoyl groups work in concert with calcium-binding sites and target proteins to guide this family of proteins to membrane-bound targets. The specific aims are: (1) Determine the molecular structure of guanylate cyclase activating photoreceptor guanylate cyclases in light-activated photoreceptors, which may serve as a molecular basis for designing therapeutics that prevent retinal degenerative diseases genetically linked to GCAPs. (2) Determine the structure of recoverin and targets bound to lipid bilayer membranes using newly developed solid-state NMR technology. The aim is to understand structural changes induced by membrane binding. (3). Elucidate the molecular interactions of Ca2+-myristoyl switch proteins bound to target proteins and discover atomic-level structural determinants important for target recognition and drug design. (4) Understand the evolutionary roots of the calcium-myristoyl switch family. The aim is to determine whether the coupling of calcium cascades to G protein cascades arose early in evolution.