Editor's Summary

6 March 2008

Cadmium fills a niche

A major part of the carbon export from the atmosphere to the deep ocean is carried out by marine phytoplankton, using carbonic anhydrase to catalyse the reversible hydration of carbon dioxide. The active site of this enzyme usually contains zinc, but some diatoms substitute cadmium — usually regarded as a toxic element — as the catalytic metal atom. The X-ray crystal structures of four forms of this enzyme from the diatom Thalassiosira weissflogii — cadmium-bound, zinc-bound, metal-free and acetate-bound — have now been determined. The enzyme can easily exchange metals at its catalytic centre, suggesting that marine diatoms use of cadmium when zinc is rare, a considerable competitive advantage in the metal-poor environment of the oceans.

Article: Structure and metal exchange in the cadmium carbonic anhydrase of marine diatoms

Yan Xu, Liang Feng, Philip D. Jeffrey, Yigong Shi & François M. M. Morel

doi:10.1038/nature06636

Abstract | Full Text | PDF (1,149K) | Supplementary information