A special type of small sulfur-rich protein, metallothioneins, have an extraordinary capability for binding heavy metals. An international team of scientists has now discovered that the marine common periwinkle, which is widely considered a delicacy, contains the largest version of the protein found yet, with one additional cadmium-binding domain and a one-third higher detoxification capacity. As they report in the journal Angewandte Chemie, this feature may help the snail survive in heavy-metal-polluted environments.
Snails and slugs are known for their intriguing ability to accumulate and detoxify heavy metals. They are even capable of discriminating between cadmium and copper, as the latter element is an indispensable element in their metabolism, while cadmium is toxic. They detoxify cadmium by binding it to metallothioneins, a class of small proteins rich in the sulfur-containing cysteine amino acid. Oliver Zerbe at the University of Zurich, Switzerland, and Reinhard Dallinger at the University of Innsbruck, Austria, and their colleagues in Barcelona, Spain, investigate the evolution of these proteins as a strategy to adapt the gastropodes to their new habitats—land snails have developed from marine species, and had to find novel strategies to cope with the higher loadings of heavy metals in the soil.
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