Conantokin G
Conantokin G is a naturally occurring 17-amino acid peptide isolated from the venom of the deadly marine cone snail Conus geographus. It has the amino acid sequence GEXXLQXNQXLIRXKSN, where X = gamma-Carboxyglutamic acid, a post-translationally modified derivative of glutamic acid with two COOH groups. It has sedative and analgesic effects in mice, acting as an NMDA [receptor antagonist].