Proteinase-activated receptor 1 (PAR1) is part of a family of G protein-coupled protease-activated receptors (PARs) involved in mediating thrombin signaling. PAR1 is activated when thrombin cleaves its NH2-terminal exodomain to reveal a new receptor NH2-terminus (beginning with the sequence SFLLRN) that is able to bind intramolecularly to the body of the receptor and effect transmembrane signaling.