Genetic Engineering of Single-Chain Gonadotropins and Hormone–Receptor Fusion Proteins

The gonadotropin hormone family is distinguished by its heterodimeric structure in which the members share a common subunit and a hormone-specific subunit. Since assembly of the heterodimer is often the rate-limiting step in production of functional hormone, single-chain hormones have been engineered by genetically linking the two subunits. The single-chain hormone can in turn be fused to its receptor to produce a functional single-chain hormone–receptor complex. These fusion constructs offer a valuable new approach in structure–function studies and in the generation of hormone analogs. In this article we describe the experimental design for the generation of single-chain human chorionic gonadotropin and single-chain hormone–receptor fusion complex and strategies for the expression of these fusion proteins.