p13 is a peptide derived from the C-terminal component which starts at the GPCR proteolysis cleavage site of GPR133. p13 specifically activates both generated chimeric P2Y12-CTF(GPR133) receptors and the wild type GPR133 receptor and is an agonist as measured by cAMP accumulation. p13 is highly selective for GPR133, and is a short tethered sequence (the Stachel sequence) within the ectodomain of GPR133, reinforcing that tethered peptide activation is a common signaling modality for the adhesion GPCR class of receptors.
