Platypus Peptides

The duck-billed platypus has to be the strangest mammal around. Native to eastern Australia, the egg-laying creature has a signature rubbery snout, tail like a beaver’s, and feet like an otter’s, and it sports an ankle spur on its hind foot that males use to deliver a shot of venom to unsuspecting victims. An international team led by Masaki Kita of Japan’s University of Tsukuba and Daisuke Uemura of Keio University, also in Japan, are now reporting new chemical details on the cocktail of peptides that give the venom its punch (J. Am. Chem. Soc. 2009, 131, 18038). Platypus venom is powerful enough to kill small animals, but luckily it causes only excruciating pain in humans that evolves into long-term pain sensitivity. The researchers previously reported that crude platypus venom potently increases Ca²⁺ concentration and disrupts the membrane in human neuroblastoma cancer cells. Guided by that finding, they used gel-permeation chromatography and mass spectrometry to purify and characterize 11 novel peptides of varying lengths in the venom. Although more studies are needed, it appears that the principal compound, a heptapeptide, takes over control of calcium ion channels. A better understanding of the peptides’ neurotoxicity could clarify the evolutionary and ecological roles of the venom and possibly lead to novel medicines, the team notes.