A key aspect PAR4 conformation in inactive platelets is ECL3 functioning as a gatekeeper, inhibiting the tethered ligand from binding to the transmembrane (TM) 3. Upon thrombin stimulation, 48Gly, on the tethered ligand, binds to 153Thr on TM3. 153Thr of TM3, TM7, and 48Gly of the tethered ligand result in receptor activation. PAR4 is now active and induces platelet activation and in vivo clot formation.