Solution structure of a core peptide derived from scyllatoxin.

An analysis of the sequences of scyllatoxin and charybdotoxin suggested that it would be possible to design a core peptide sequence which would still fold to give the beta-hairpin and helix seen in the toxins, but which would eliminate one disulfide and connecting residues. The core sequence was modeled, then synthesized and purified. The cysteines oxidize in air to give the same disulfide pairings as seen in the parent toxins as the major product. The three-dimensional structure of the core sequence peptide, termed Max, was determined using proton NMR spectroscopy and found to be identical in secondary structure to the toxins. However differences were found in the relative orientation of the beta-hairpin and helix. The use of this structural motif, found in many insect toxins, as a disulfide framework for exploring sequence/structure/activity relationships is discussed.