THE CRYSTAL-STRUCTURE OF HUMAN ENDOTHELIN

The three-dimensional structure of the vasoactive polypeptide endothelin, the most potent vasocontrictor yet identified, has keen determined by X-ray crystallography to 2.18 Angstrom resolution. This intermediate-sited structure was solved by molecular replacement techniques using a fragment of an NMR-derived model for initial phasing of the data. However, comparisons of the final X-ray structure with the many diverse models derived from NMR data indicate some important differences, especially in the carboxy-terminal region of the molecule: the entire carboxy terminal tail (residues 16-21) is helical in the crystal structure, but not in any of the NMR structures. This may be a functionally significant difference as this region is crucial for receptor binding and vasoactivity.