Many therapeutic agents work by modifying, interfering with, or inactivating cellular proteins.
Among the top 25 pharmaceuticals, one-third act on proteins embedded in cell membranes. These proteins include the molecular receptors through which cells interact with and respond to extracellular effectors. These receptors play central roles in cardiovascular disease, pain, schizophrenia, and many other pathologic processes. This same class of proteins is exceedingly difficult to isolate in quantity, and attempts to crystallize these proteins have been unsuccessful. This is a problem, because drug discovery efforts increasingly depend upon detailed knowledge of the molecular structure of proteins provided by X-ray crystallography.