Immunological and structural characterization of sarafotoxin/endothelin family of peptides

A highly specific and sensitive radioimmunoassay (RIA) was developed for the potent vasoconstrictor peptides, sarafotoxin-b and human endothelin. The antigenic determinants of the antibodies employed in studies with these assays were found to be localized within the amino acid sequence at positions 4-7. This was confirmed by CNBr cleavage of the methionyl residue at position 6 in the sarafotoxin and at position 7 in the endothelin. The chemically characterized modified peptides showed very low cross reactivity in the RIAs. On the other hand, the binding properties as well as the ability to induce phosphoinositide hydrolysis were very similar in the modified and native peptides, indicating that despite cleavage of the peptide bond the biologically active conformation responsible for either binding or phosphoinositide hydrolysis is retained, probably because of the disulfide bonds. Thus, structural alteration might be a valuable means of curtailing some of the various activities induced by the sarafotoxin/endothelin family of peptides.