CYSTEINE PAIRING IN THE GLYCOPROTEIN-IIBIIIA ANTAGONIST KISTRIN USING NMR, CHEMICAL-ANALYSIS, AND STRUCTURE CALCULATIONS

The pairing of the cysteines indisulfide bonds was investigated for the 68-residue RGD-containing protein kistrin, a potent antagonist of the integrin GP IIbIIIa and an inhibitor of platelet aggregation. Kistrin belongs to a family of homologous proteins found in snake venoms termed disintegrins, all of which have a cysteine content. The disulfide pairing of the 2 cysteines was investigated by chemical analysis, NMR spectroscopy, and distance geometry calculations. The data show that the disulfide pairs are 4-19, 6-14, 13-36, 27-33, 32-57, and 45-64. The various means for assigning the disulfide bonds are described, and the results are compared with the cysteine pairings reported for other disintegrin proteins.