| Abstract: | Using the crystal structure of cobra venom cardiotoxin as a templet, a computer designed peptide with a novel conformation and biological activity has been synthesized chemically. The designed peptide utilized two calcium coordination sites instead of disulfide bridges to hold the conformation. The coordination sites were introduced at the cleft of three β-sheet strands by replacing the residues of Leu-1, Leu-26, Ser-28, Leu-48, and Ser-55 with Glu and using their γ-carboxyl groups as legends. The residues of Cys at positions 3, 14, 21, 38, 42, 53, 54, and 59 of the four disulfide bridges were changed with Gly to remove all the disulfide bonds. Circular dichroism spectra showed that the synthesized peptide has a conformation similar to that of the native cardiotoxin of a defined structure only in aqueous solutions with the presence of calcium ions. Immunoprecipitation assay, using the anti-cardiotoxin V, showed that in the presence of calcium ion the peptide had same cross reaction as that of native cardiotoxin. Hemolysis assay in the presence of calcium ion (150–250 mmol) and phospholipase A2 showed that the peptide had 65–70% as much cytolytic activity as the native toxin. |
