Few things are more frustrating than a locked door for which one can find no key.
Receptors are molecules to which intercellular signaling molecules bind in a very specific manner, much like keys in a lock. Scientists predict that of the roughly 80,000 genes that constitute the human genome, more than 300 encode G protein-coupled receptors. Finding the ligand that binds to a receptor is important because, without it, one cannot determine the receptor's function. We thought they would be a gold mine for discovering new receptors that might be targets for developing new drugs. G protein-coupled receptors are particularly attractive drug targets because they control an enormous variety of cellular functions.