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Differential reactivity of individual zinc ions in clusters from bacterial metallothioneins
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Leszczyszyn, Oksana I., Evans, Christine D., Keiper, Stella E., Warren, Gernma Z. L. and Blindauer, Claudia A. (2007) Differential reactivity of individual zinc ions in clusters from bacterial metallothioneins. Inorganica Chimica Acta, Volume 360 (Number 1). pp. 3-13. doi:10.1016/j.ica.2006.08.015
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Official URL: http://dx.doi.org/10.1016/j.ica.2006.08.015
Abstract
The bacterial metallothionein SmtA binds four zinc ions with high affinity and specificity in a Zn4S9N2 cluster. We have explored the reactivity of these zinc ions towards the metal-chelator EDTA. Under pseudo-first-order conditions, initial break-down of zinc-thiolate bonds is rapid, followed by several slower phases. The reaction with stoichiometric amounts of EDTA is relatively slow and has been followed by H-1 NMR and mass spectrometry. Both methods reveal that partially metallated intermediates occur during the reaction. Three- and two-metal species are observed in only minor amounts, whereas the Zn-1 species is dominant during the mid stages of the reaction, before complete metal depletion occurs. These results suggest that the zinc finger site in SmtA is not only inert towards metal exchange, but also more resilient towards chelating agents. The greater inertness of this site may help to maintain the protein fold during metal depletion, and allow subsequent facile metal uptake. Conversely, it is likely that the protein fold is the major contributor to the observed persistence of Zn(1)SmtA in this reaction. Mass spectrometric studies with His-to-Cys mutants of SmtA reveal that the primary site for EDTA attack is the His49-containing zinc site C, and that His40 has a major influence on the reactivity of three sites.
| Item Type: | Journal Article | ||||||||||
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| Subjects: | Q Science > QD Chemistry | ||||||||||
| Divisions: | Faculty of Science > Chemistry | ||||||||||
| Journal or Publication Title: | Inorganica Chimica Acta | ||||||||||
| Publisher: | Elsevier BV | ||||||||||
| ISSN: | 0020-1693 | ||||||||||
| Official Date: | 1 January 2007 | ||||||||||
| Dates: |
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| Volume: | Volume 360 | ||||||||||
| Number: | Number 1 | ||||||||||
| Number of Pages: | 11 | ||||||||||
| Page Range: | pp. 3-13 | ||||||||||
| DOI: | 10.1016/j.ica.2006.08.015 | ||||||||||
| Status: | Peer Reviewed | ||||||||||
| Publication Status: | Published | ||||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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