Ligand binding analysis of human neuropeptide Y1 receptor mutants expressed in E. coli

Site-directed mutants of the human neuropeptide Y1 (NPY Y1) receptor expressed as a maltose binding protein fusion protein in E. coli show identical ligand binding parameters compared with the same mutants expressed in mammalian cells using a vaccinia virus expression system. However, it was remarkable that two receptor mutants, which were initially classified as non-binding when expressed in an eukaryotic expression system, could actually be revealed to have wild-type binding activity when expressed in E. coli. Re-expression and retesting of these mutants in mammalian cells confirmed this result. This shows that bacterial expression can be used as a fast, versatile and valuable alternative to mammalian expression systems for the analysis of ligand binding sites in G-protein coupled receptors.