Zeitoun-Ghandour, Sukaina, Charnock, John M., Hodson, Mark E., Leszczyszyn, Oksana I., Blindauer, Claudia A. and Sturzenbaum, Stephen R.. (2010) The two Caenorhabditis elegans metallothioneins (CeMT-1 and CeMT-2) discriminate between essential zinc and toxic cadmium. The FEBS Journal, Vol.277 (No.11). pp. 2531-2542. ISSN 1742-464X

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Abstract

The nematode Caenorhabditis elegans expresses two metallothioneins (MTs), CeMT-1 and CeMT-2, that are believed to be key players in the protection against metal toxicity. In this study, both isoforms were expressed in vitro in the presence of either Zn(II) or Cd(II). Metal binding stoichiometries and affinities were determined by ESI-MS and NMR, respectively. Both isoforms had equal zinc binding ability, but differed in their cadmium binding behaviour, with higher affinity found for CeMT-2. In addition, wild-type C. elegans, single MT knockouts and a double MT knockout allele were exposed to zinc (340 mu m) or cadmium (25 mu m) to investigate effects in vivo. Zinc levels were significantly increased in all knockout strains, but were most pronounced in the CeMT-1 knockout, mtl-1 (tm1770), while cadmium accumulation was highest in the CeMT-2 knockout, mtl-2 (gk125) and the double knockout mtl-1;mtl-2 (zs1). In addition, metal speciation was assessed by X-ray absorption fine-structure spectroscopy. This showed that O-donating, probably phosphate-rich, ligands play a dominant role in maintaining the physiological concentration of zinc, independently of metallothionein status. In contrast, cadmium was shown to coordinate with thiol groups, and the cadmium speciation of the wild-type and the CeMT-2 knockout strain was distinctly different to the CeMT-1 and double knockouts. Taken together, and supported by a simple model calculation, these findings show for the first time that the two MT isoforms have differential affinities towards Cd(II) and Zn(II) at a cellular level, and this is reflected at the protein level. This suggests that the two MT isoforms have distinct in vivo roles.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QL Zoology
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Chemical affinity, Cadmium, Metallothionein, Zinc, Caenorhabditis elegans, Speciation (Chemistry)
Journal or Publication Title:	The FEBS Journal
Publisher:	Wiley-Blackwell Publishing Ltd.
ISSN:	1742-464X
Date:	June 2010
Volume:	Vol.277
Number:	No.11
Number of Pages:	12
Page Range:	pp. 2531-2542
Identification Number:	10.1111/j.1742-4658.2010.07667.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Royal Society (Great Britain), Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC), Science and Technology Facilities Council (STFC)
Grant number:	BB/E025099 (BBSRC), BB/E05099 (STFC)
URI:	http://wrap.warwick.ac.uk/id/eprint/5866

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