Disulfide pairings in geographutoxin I, a peptide neurotoxin from Conus geographus.

The three intramolecular disulfide linkages of geographutoxin I, a peptide neurotoxin isolated from the venom of the marine snail Conus geographus, were examined by a novel method for determination of the positions of disulfide linkages in peptides [(1989) Bull. Chem. Soc. Jp. 62, 1986-1994]. The disulfide bridges were found to be between Cys3 and Cys15, Cys4 and Cys20, and Cys21, indicating that geographutoxin I has a rigid conformation consisting of three loops stabilized by these three disulfide linkages.