RT Journal Article SR Electronic T1 Binding of a Thrombin Receptor Tethered Ligand Analogue to Human Platelet Thrombin Receptor JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 350 OP 356 DO 10.1124/mol.51.2.350 VO 51 IS 2 A1 Ho-Sam Ahn A1 Carolyn Foster A1 George Boykow A1 Leyla Arik A1 April Smith-Torhan A1 David Hesk A1 Meeta Chatterjee YR 1997 UL http://molpharm.aspetjournals.org/content/51/2/350.abstract AB A thrombin receptor-radioligand binding assay was developed using [3H]A(pF-F)R(ChA)(hR)Y-NH2([3H]haTRAP), a high affinity thrombin receptor-activating peptide (TRAP), and human platelet membranes. Scatchard analysis of saturation binding data indicated that [3H]haTRAP bound to platelet membranes with aK d of 15 nm and a B max of 5.2 pmol/mg of protein. The binding was reduced by GPPNHP, a nonmetabolizable GTP analogue. Various TRAPs and a TRAP antagonist, but not other receptor agonists, displaced [3H]haTRAP from the binding sites. SFLLRN-NH2, a thrombin receptor-tethered ligand analogue, and [3H]haTRAP exhibited competitive binding for the same binding sites. The relative affinity of these peptides for the binding site paralleled their EC50 or IC50 values for platelet aggregation. These data indicate that [3H]haTRAP binds specifically and saturably to the functioning G protein-linked thrombin (tethered ligand) receptor in human platelet membranes.