Engineering a soluble parathyroid hormone GPCR mimetic

We designed and characterized a soluble mimic of the parathyroid hormone (PTH) receptor (PTH1R) that incorporates the N‐terminus and third extracellular loop of PTH1R, important for ligand binding. The engineered receptor (PTH1R‐NE3) was conceived to enable easy production and the use of standard biochemical and biophysical assays for the screening of competitive antagonists of PTH. We show that PTH1R‐NE3 is folded, thermodynamically stable and selectively binds PTH. We also demonstrate the utility of our mimic by identifying a small molecule that competes with PTH in our PTH1R‐NE3‐based fluorescence polarization assay. Antagonists to PTH1R, a transmembrane protein belonging to the class B G‐protein coupled receptor family, may provide new therapeutic options for calcium metabolism diseases like humoral hypercalcemia of malignancy. Proteins 2014; 82:1370–1375. © 2013 Wiley Periodicals, Inc.