This project is to characterize the gene and protein structure and evolution of neurotransmitter receptors belonging to two major multigene families. The first gene family comprises adrenergic, muscarinic, opsin, serotonin and octopamine receptors and the second comprises nicotinic cholinergic, GABA/benzodiazepine NMDA, and glycine receptors. The specific aims are to clone and sequence the genes for receptors in these two multigene families; to obtain high density receptor expression and to use the expressed proteins to determine the complete receptor structure in part by computer enhanced molecular modeling; to determine the evolution of the neurotransmitter receptor gene families; and to search for and characterize receptor gene polymorphisms. To date, we have cloned and sequenced a significant number of receptor genes from both multigene families. These include several alpha and beta-adrenergic receptors from human and rat cDNA and genomic libraries; muscarinic cholinergic receptor from human, rat and Drosophila genomic libraries. Octopamine receptors for Drosophila; human alpha and beta subunits of the GABA/benzodiazepine receptor; and nicotinic receptors from locusts and C. elegans. For example the human GABA beta 1 subunit has been cloned and sequenced and localized to chromosome 4. This gene is over 65kb and is composed of nine exons. The exons and splice sites are highly conserved in other GABA receptor subunits from humans and lower species. Permanent cell lines expressing the unique neurotransmitter receptor proteins are providing key new information concerning the mechanism of receptors activation by neurotransmitters.