Many inherited diseases, including cystic fibrosis, diabetes, and familial hypercholesterolemia are caused by mutations that impair the folding and intracellular trafficking of ion channels, transporters and receptors that are normally expressed at the plasma membrane. There is compelling evidence demonstrating that the mutant phenotype of many of these mutants can be suppressed by treatment with pharmacological chaperones, small high affinity ligands that bind to and stabilize the native 3-dimensional structure of their respective targets. To develop pharmacological chaperones with therapeutic potential, it is necessary to identify small high affinity ligands that can stabilize the native state for proteins without known high affinity ligands. The exploratory project described here is aimed at the development of a general, robust cell based assay that can be used in highthroughput screening platforms to identify novel pharmacological chaperones based on their ability to increase the efficiency of protein folding. This homogenous assay exploits a highly sensitive enzymatic complementation between a small peptide (S-peptide) and RNAseA and the use of a fluorogenic substrate. It is proposed to demonstrate the feasibility of this assay with two model substrate, the G-protein coupled V2 vasopressin receptor, mutations in which are linked to nephrogenic diabetes insipidus and the cystic fibrosis transmembrane conductance regulator.