PAR peptides (TRAP peptides and thrombin receptor-like peptides) activate the proteinase-activated receptors PAR-1 to PAR-4.

PAR-1 peptides are also called TRAP peptides (thrombin receptor-activating peptides).

Cloning and expression of a functional human thrombin receptor have revealed a protein with seven transmembrane domains and a large extracellular amino-terminal extension. Thrombin cleaves within this extension, thereby creating a new receptor amino-terminus that functions as a tethered ligand and activates the receptor. A 14-amino acid peptide mimicking this new amino-terminus has been found to be a potent thrombin receptor activator as well as an effective agonist for platelet activation.