Endothelin-receptor interactions: Role of a putative sulfhydryl on the endothelin receptor

Abstract

The mechanism of action of endothelin-receptor interactions was studied, using radioligand binding assays and SDS-PAGE, to investigate the possibility of disulfide interchange. Electrophoretic analysis suggested involvement of disulfide bond(s) in the receptor-ligand complex. Treatment of Et receptors with sulfhydryl-specific alkylating reagents (NEM or others) resulted in decreased ability to bind [ 125I]Et-1. [Dpr 1-Asp 15]Et-1, an antagonist homologous to Et but with an amide link replacing one of the disulfides, bound to Et receptors reversibly, but binding of Et-1 was less reversible. Preincubation of receptors with Et-L, but not with [Dpr 1-Asp 15]Et-L, protected receptors from alkylation with [ 14C]NEM. The data suggest that the Et receptor has a sulfhydryl group at or near the Et binding site. A model is proposed in which the role of the putative sulfhydryl group is discussed.