Solution structure determination of endothelin-1 in methanol/water by NMR and molecular modelling methods

To understand the structural requirements for the biological activity of endothelin peptides and to develop receptor selective endothelin analogues further, the solution structure of the bicyclic 21 amino acid residue vasoactive peptide, endothelin-1, has been determined in methanol-d₃/water using high-resolution¹H-NMR spectroscopy. To our knowledge, this solvent system has not previously been used in NMR studies of endothelin and/or endothelin-like peptides. Two-dimensional DQFCOSY, TOCSY and NOESY spectra were acquired along with a series of one-dimensional spectra. A total of 219 distance constraints and 5 angle constraints were derived from the NMR data. These were incorporated into structure calculations using distance geometry (DIANA) followed by simulated annealing and molecular dynamics. The resulting structures are characterized by an α-helical conformation, Lys⁹-His¹⁶, and residues Ser⁵-Asp⁸ form a type I β-turn. The N-terminal region, which was not extensively constrained by NMR data, showed no preferred conformation. The C-terminal tail showed less extensive conformational averaging but no descriptive conformation could be observed. The results obtained in this study are in good agreement with previous proposals.