This domain superfamily is found in the extracellular part of some of the secretin-like (family 2) GPCRs including the corticotropin releasing factor receptor 1; calcitonin receptor; diuretic hormone receptor; glucagon-like peptide 1 receptor; and parathyroid hormone peptide receptor. The N-terminal extracellular domain is the major ligand recognition domain. This domain structure has a disulfide-rich all-beta fold and contains a beta sandwich of 5 strands.