TY - JOUR
T1 - Structure and metal exchange in the cadmium carbonic anhydrase of marine diatoms
AU - Xu, Yan
AU - Feng, Liang
AU - Jeffrey, Philip D.
AU - Shi, Yigong
AU - Morel, Francois M. M.
PY - 2008/3/6
Y1 - 2008/3/6
N2 - Carbonic anhydrase, a zinc enzyme found in organisms from all kingdoms, catalyses the reversible hydration of carbon dioxide and is used for inorganic carbon acquisition by phytoplankton. In the oceans, where zinc is nearly depleted, diatoms use cadmium as a catalytic metal atom in cadmium carbonic anhydrase (CDCA). Here we report the crystal structures of CDCA in four distinct forms: cadmium-bound, zinc-bound, metal-free and acetate-bound. Despite lack of sequence homology, CDCA is a structural mimic of a functional β-carbonic anhydrase dimer, with striking similarity in the spatial organization of the active site residues. CDCA readily exchanges cadmium and zinc at its active site - an apparently unique adaptation to oceanic life that is explained by a stable opening of the metal coordinating site in the absence of metal. Given the central role of diatoms in exporting carbon to the deep sea, their use of cadmium in an enzyme critical for carbon acquisition establishes a remarkable link between the global cycles of cadmium and carbon.
AB - Carbonic anhydrase, a zinc enzyme found in organisms from all kingdoms, catalyses the reversible hydration of carbon dioxide and is used for inorganic carbon acquisition by phytoplankton. In the oceans, where zinc is nearly depleted, diatoms use cadmium as a catalytic metal atom in cadmium carbonic anhydrase (CDCA). Here we report the crystal structures of CDCA in four distinct forms: cadmium-bound, zinc-bound, metal-free and acetate-bound. Despite lack of sequence homology, CDCA is a structural mimic of a functional β-carbonic anhydrase dimer, with striking similarity in the spatial organization of the active site residues. CDCA readily exchanges cadmium and zinc at its active site - an apparently unique adaptation to oceanic life that is explained by a stable opening of the metal coordinating site in the absence of metal. Given the central role of diatoms in exporting carbon to the deep sea, their use of cadmium in an enzyme critical for carbon acquisition establishes a remarkable link between the global cycles of cadmium and carbon.
UR - http://www.scopus.com/inward/record.url?scp=40449131050&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=40449131050&partnerID=8YFLogxK
U2 - 10.1038/nature06636
DO - 10.1038/nature06636
M3 - Article
C2 - 18322527
AN - SCOPUS:40449131050
VL - 452
SP - 56
EP - 61
JO - Nature
JF - Nature
SN - 0028-0836
IS - 7183
ER -