G protein coupled receptors (GPCRs) play critical roles in animal development, cell growth, immune function, and plant defense. Unfortunately, identifying ligands for these cell surface receptors has proven extraordinarily challenging. This project proposes to develop a novel system for addressing this challenge. The system employs a novel class of DNA-protein hybrid molecules as the foundation of a powerful protein display technology. It is based on the observation that VirD2 protein of the bacterial plant pathogen, Agrobacterium tumefaciens, has the remarkable capacity to covalently couple itself to specific DNA recognition sequences. Hence, VirD2 may constitute a generic and versatile tool for covalently linking proteins of interest to the genes that encode them. Such molecules will then be used to generate libraries of DNA-protein hybrids. The small size and biochemical simplicity of the proposed DNA-protein hybrids are expected to overcome biophysical constraints that severely limit the usefulness of "classical" phage and cell-based display systems for GPCR studies. It is expected that the proposed system will have a substantial impact on elucidating GPCR function and biology. Additionally, graduate and postdoctoral students will be trained.
