Thrombin receptor

There are three known thrombin receptors termed PAR1, PAR3 and PAR4 (PAR for protease-activated receptor). There are three known thrombin receptors termed PAR1, PAR3 and PAR4 (PAR for protease-activated receptor). These receptors are members of the 7 transmembrane g protein-coupled family of receptors, however, their method of activation is unique. Thrombin, a serine protease, binds to and cleaves the extracellular N-terminal domain of the receptor. A tethered ligand corresponding to the new N-terminus, SFLLRN, is then unmasked, binding to the second extracellular loop of the receptor and activating it.