Conformational stability of the endothelin/sarafotoxin family of peptides.

There are significant differences between the structures reported for members of the endothelin/sarafotoxin family of peptides, but also for the same peptides studied by different groups, raising the possibility that some of the differences are attributable to variation in solution conditions rather than intrinsic structural heterogeneity. We have shown, using circular dichroism spectroscopy and equilibrium sedimentation, that the secondary structures of these peptides are little affected by wide variations in pH, or by self-association. Although acetonitrile has a pronounced effect on the extent of peptide self-association it does not appear to alter the backbone structure of sarafotoxin SRTb, and has only minor effects on endothelin-1 and endothelin-3. The observed conformational variation thus appears largely to reflect sequence-dependent differences.