IsCT, a novel cytotoxic linear peptide from scorpion Opisthacanthus madagascariensis

A novel cytotoxic linear peptide, IsCT, was characterized from scorpion Opi sthacanthus madagascariensis. It is a linear peptide with a molecular weigh t of 1501.9 Da composed of 13 amino acid residues without cysteines. MS/MS analysis showed that its C-terminal is amidated. The identity of IsCT is re -confirmed by comparing the chemical synthesized peptide with the natural o ne. IsCT demonstrated antimicrobial activity against both gram-positive and gram-negative bacteria and hemolytic activity to sheep red blood cells. Al so, it can release histamine from rat peritoneal mast cells. The CD absorpt ion suggested that IsCT had an alpha -helix configuration in aqueous TFE. I sCT is one of the shortest natural cytotoxic peptides described, and it wil l be a suitable model for studying peptide-lipid interactions. (C) 2001 Aca demic Press.