A DETERMINATION OF THE SOLUTION CONFORMATION OF THE NONMAMMALIAN TACHYKININ ELEDOISIN BY NMR AND CD SPECTROSCOPY

The nonmammalian tachykinin eledoisin was investigated by use of CD an d two-dimensional NMR techniques. In aqueous solution the peptide is c onformationally averaged, but on addition of 50% trifluoroethanol (TFE ) or sodium dodecyl sulfate (SDS) it adopts an ct-helical structure. I n TFE/H2O and SDS, residues 6-10 of eledoisin show more conformational order than the terminal regions, which undergo dynamic fraying. A pos sible turn in the N-terminal ''address'' region, the putative receptor recognition site of the peptide, is detected by NMR spectroscopy but appears to undergo substantial conformational averaging. The NMR data indicate that the helical central core of eledoisin is better defined in the micellar environment than in TFE; however, partial unfolding vi a 3(10) intermediates occurs in both cases. The conformational prefere nce for SDS-bound eledoisin was examined by three-dimensional structur e calculations using NMR-derived distance information in simulated ann ealing calculations.