SOLUTION STRUCTURE OF ENDOTHELIN-B RECEPTOR-SELECTIVE ANTAGONIST RES-701-1 DETERMINED BY H-1-NMR SPECTROSCOPY

The three-dimensional structure of the endothelin B receptor (ET(B)) selective antagonist RES-701-1 has been determined by H-1 NMR in deuterated dimethyl sulphoxide. RES-701-1 consists of 16 amino acid residues with a novel internal linkage between the beta-carboxyl group of Asp9 and the alpha-amino group of Gly1. The structural calculations were carried out with the combined use of distance geometry and simulated annealing. The result indicates that RES-701-1 adopts an extraordinary folding; the 'tail' (Trp10-Trp16) passes through the 'ring' region (Gly1-Asp9). Several critical NOEs directly support this extraordinary folding. The folding of RES-701-1 turned out to be the same as that Frechet et al. calculated for RP 71955 which possesses the same internal linkage as RES-701-1. The obtained structure suggested that the region consisting of Thr6, Ala7, Tyr14 and Tyr15 and/or, the region consisting of Asn2, Tyr14 and Tyr15 are involved in a binding with ET(B).