COILED-COIL MOLECULAR RECOGNITION - DIRECTED SOLUTION ASSEMBLY OF RECEPTOR ECTODOMAINS

The high affinity interleukin-2 (IL-2) receptor is composed of at leas t three cell surface proteins (alpha, beta and gamma subunits), each o f which is independently capable of ligand binding. Physiologically, t hese subunits cooperate to form dimeric and trimeric complexes that ef ficiently capture IL-2 and transmit the signal across the membrane. Th e knowledge of how each subunit functions with respect to ligand captu re, signal transmission and internalization is essential for the devel opment of ligand-based IL-2 agonists and antagonists, as well as recep tor-related therapeutic and diagnostic reagents. Only one of the subun its (p55 or alpha chain) is capable of interacting with ligand in solu tion in a manner that resembles cell surface binding. To generate solu ble multimeric complexes of the IL-2 receptor subunits that may bind l igand in solution in a fashion that mimics the same receptor complexes on the cell surface, we have added recognition sequences (coiled-coil heptad repeats) to the ectodomains of the individual receptors. Here we describe the expression and characterization of a prototype IL-2 be ta receptor ectodomain coiled-coil fusion protein and demonstrate that this is a feasible approach to the preparation of cytokine receptor s olution complexes.