Primary structure of Stoichactis helianthus cytolysin III.

The primary structure of Stoichactis helianthus cytolysin III has been determined by automated Edman degradation of the intact protein and of peptides derived therefrom by hydrolysis with trypsin and staphylococcal protease and by chemical cleavage with cyanogen bromide and o-iodosobenzoic acid. As a result of these studies, the positions of all 153 amino acid residues of toxin III have been unambiguously determined. Most regions of sequence were determined two times in different types of digests of the protein. A number of highly hydrophobic regions of sequence, which may be functionally significant, have been identified, including a region rich in tyrosine and tryptophan (residues 86-98). The secondary structure of toxin III has been predicted by Chou-Fasman analysis (Chou, P.Y., and Fasman, G.D. (1978) Annu. Rev. Biochem. 47, 251-276) of the primary structure. The predicted secondary structure contains 16% alpha-helix and 31% beta-structure.