A peptide of nine amino acid residues from alpha-sarcin cytotoxin is a membrane-perturbing structure.

A water-soluble synthetic peptide with only nine amino acid residues, comprising the 131-139 sequence region of the cytotoxic protein alpha-sarcin (secreted by the mold Aspergillus giganteus), interacts with large unilamellar vesicles composed of acid phospholipids. It promotes lipid mixing between bilayers and leakage of vesicle aqueous contents, and it also abolishes the phospholipid phase transition. Other larger peptides containing such an amino acid sequence also produce these effects. These peptides acquire alpha-helical conformation in the presence of trifluoroethanol, but display beta-strand conformation in the presence of sodium dodecyl sulfate. The interaction of these peptides with the lipid vesicles also results in beta-structure. The obtained data are discussed in terms of the involvement of the 131-139 stretch of alpha-sarcin in its interaction with lipid membranes.