A Fully Automated [35S]GTPγS Scintillation Proximity Assay for the High-Throughput Screening of Gi-Linked G Protein-Coupled Receptors

The diversity of physiological functions mediated by the GPCR superfamily provides a rich source of molecular targets for drug discovery programs. Consequently, a variety of assays have been designed to identify lead molecules based on ligand binding or receptor function. In one of these, the binding of [35S]GTPγS, a nonhydrolyzable analogue of GTP, to receptor-activated G-protein α subunits represents a unique functional assay for GPCRs and is well suited for use with automated HTS. Here we compare [35S]GTPγS scintillation proximity binding assays for two different Gi-coupled GPCRs, and describe their implementation with automated high-throughput systems.