Endothelins are endothelium-derived vasoactive peptides involved in a variety of biological functions. The active form of this protein is a 21 amino acid peptide processed from the precursor protein. This 21 residue peptide (ET-3) is a member of a family of potent vasoconstrictors namely, Endothelin and Sarafotoxin. The active peptide is a ligand for endothelin receptor type B (EDNRB). The interaction of this endothelin with EDNRB is essential for development of neural crest-derived cell lineages, such as melanocytes and enteric neurons. ET-3 is a less potent vasoconstrictor than ET-1 also varying by 6 amino acids in sequence homology.