The peptide is Exendin-4 labeled with fluorescein at the tryptophan residue. FLEX is equipotent with GLP-1(7-36)-amide and exendin-4. It is an inhibitor of [125I]GLP-1 binding to the human GLP-1 receptor stably expressed in CHO cells, and stimulates these cells The accumulation of cAMP to maintain the complete biological potency and efficacy. The flexible combination with CHO/hGLP-1R film leads to an increase in fluorescence anisotropy. This binding is specific and saturable (Kd=2.0+/-0.4nm). GLP-1(7-36)-amide and Exendin-4 are isopotential inhibitors of flexible binding of human GLP-1 receptor. Therefore, FLEX is an effective biologically active ligand that can be used to study the binding and functional properties of human GLP-1 receptors.
Chicchi, GG. et al. Peptides 18, 319 (1997), doi: 10.1016/S0196-9781(96)00320-8
H - His - Gly - Glu - Gly - Thr - Phe - Thr - Ser - Asp - Leu - Ser - Lys - Gln - Met - Glu - Glu - Glu - Ala - Val - Arg - Leu - Phe - Ile - Glu - (Trp - S - FAM) - Leu - Lys - Asn - Gly - Gly - Pro - Ser - Ser - Gly - Ala - Pro - Pro - Pro - Ser - NH2