A new pathway for heavy metal detoxification in animals - Phytochelatin synthase is required for cadmium tolerance in Caenorhabditis elegans

Increasing emissions of heavy metals such as cadmium, mercury, and arsenic into the environment pose an acute problem for all organisms. Consideration s of the biochemical basis of heavy metal detoxification in animals have fo cused exclusively on two classes of peptides, the thiol tripeptide, glutath ione (GSH, gamma -Glu Cys-Gly), and a diverse family of cysteine-rich low m olecular weight proteins, the metallothioneins. Plants and some fungi, howe ver, not only deploy GSH and metallothioneins for metal detoxification but also synthesize another class of heavy metal binding peptides termed phytoc helatins (PCs) from GSH. Here we show that PC-mediated heavy metal detoxifi cation is not restricted to plants and some fungi but extends to animals by demonstrating that the ce-pcs-l gene of the nematode worm Caenorhabditis e legans encodes a functional PC synthase whose activity is critical for heav y metal tolerance in the intact organism.