Structure-activity relationships of endothelin: Importance of the C-terminal moiety

The vasoconstrictor activities of various forms of derivatives of endothelin (ET) were characterized in vitro by measuring the contraction of porcine coronary artery strips. The removal of the C-terminal Trp 21 reduced the molar potency of the peptide by nearly 3 orders of magnitude. The removal of amino acid residues from the C-terminus of ET(1–20) further attenuated the activity. Replacement of Trp 21 with D-Trp, reduction and carboxamidomethylation of the four Cys residues, or cleavage at Lys 9 by lysyl endopeptidase all lowered the potency approximately 200 fold. While both native ET and [D-Trp 21]ET induced a very slow and sustained vasoconstriction, the other derivatives of ET listed above showed a much more rapid kinetics of vasoconstriction. These results indicate that the C-terminal Trp of ET is especially important for the potent and extremely long-lasting vasoconstrictor activity characteristic to ET.