Nucleic Acids Research Advance Access originally published online on April 13, 2008
Nucleic Acids Research 2008 36(9):3128-3138; doi:10.1093/nar/gkn103
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Nucleic Acids Research, 2008, Vol. 36, No. 9 3128-3138
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Structural Biology |
Copper sensing function of Drosophila metal-responsive transcription factor-1 is mediated by a tetranuclear Cu(I) cluster
1Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA, 2Institute of Molecular Biology, University of Zurich, Winterhurerstrasse 190, 8057 Zurich, Switzerland, 3Department of Geological Sciences, University of Saskatchewan, Saskatoon, S7N 5E2, Canada and 4Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
*To whom correspondence should be addressed. Tel: +41 1 635 3140; Fax: +41 1 635 6811; Email: walter.schaffner{at}molbio.uzh.ch Correspondence may also be addressed to David P. Giedroc. Tel: +1 812 856 5449; Fax: +1 812 855 8300; Email: giedroc{at}indiana.edu
Received January 3, 2008. Revised February 21, 2008. Accepted February 25, 2008.
Drosophila melanogaster MTF-1 (dMTF-1) is a copper-responsive transcriptional activator that mediates resistance to Cu, as well as Zn and Cd. Here, we characterize a novel cysteine-rich domain which is crucial for sensing excess intracellular copper by dMTF-1. Transgenic flies expressing mutant dMTF-1 containing alanine substitutions of two, four or six cysteine residues within the sequence 547CNCTNCKCDQTKSCHGGDC565 are significantly or completely impaired in their ability to protect flies from copper toxicity and fail to up-regulate MtnA (metallothionein) expression in response to excess Cu. In contrast, these flies exhibit wild-type survival in response to copper deprivation thus revealing that the cysteine cluster domain is required only for sensing Cu load by dMTF-1. Parallel studies show that the isolated cysteine cluster domain is required to protect a copper-sensitive S. cerevisiae ace1
strain from copper toxicity. Cu(I) ligation by a Cys-rich domain peptide fragment drives the cooperative assembly of a polydentate [Cu4-S6] cage structure, characterized by a core of trigonally S3 coordinated Cu(I) ions bound by bridging thiolate ligands. While reminiscent of Cu4-L6 (L = ligand) tetranuclear clusters in copper regulatory transcription factors of yeast, the absence of significant sequence homology is consistent with convergent evolution of a sensing strategy particularly well suited for Cu(I).
The authors wish it to be known that, in their opinion, the first three authors should be regarded as joint First Authors.