Fluorescein-Trp25-Exendin-4

This peptide is Exendin-4 labeled with fluorescein at the Tryptophan residue. FLEX is equipotent to GLP-1(7-36)-amide and exendin-4 as an inhibitor of [125I] GLP-1 binding to the human GLP-1 receptor stably expressed in CHO cells, and maintains full biological potency and efficacy as measured by the stimulation of cAMP accumulation in these cells. FLEX binding to CHO/hGLP-1R membranes results in an increase in fluorescence anisotropy. The binding is specific and saturable (Kd = 2.0 +/- 0.4 nM), and GLP-1(7-36)-amide and Exendin-4 are equipotent inhibitors of FLEX binding to the human GLP-1 receptor. Thus, FLEX is a potent, biologically active ligand that is useful for the study of the binding and functional characteristics of the human GLP-1 receptor.