Production and use of trimeric isoleucine zipper fusion proteins to study surface receptor ligand interactions.

Soluble recombinant forms of surface receptors are commonly used to study the interaction between cell surface receptors and their ligands. By fusing the extracellular domain of the receptor to an isoleucine zipper (ILZ) sequence, it is possible to generate recombinant receptor fusion proteins that form trimers in solution. These ILZ fusion proteins demonstrate several advantages over the commonly used Fc fusion proteins. This unit describes the production and purification of recombinant ILZ fusion proteins. A protocol is also provided for the use of ILZ fusion proteins to study cell surface receptor-ligand interactions on intact cells by flow cytometry.