Copper sensing function of Drosophila metal-responsive transcription factor-1 is mediated by a tetranuclear Cu(I) cluster.
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 (547)CNCTNCKCDQTKSCHGGDC(565) 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 ace1Delta strain from copper toxicity. Cu(I) ligation by a Cys-rich domain peptide fragment drives the cooperative assembly of a polydentate [Cu(4)-S(6)] cage structure, characterized by a core of trigonally S(3) coordinated Cu(I) ions bound by bridging thiolate ligands. While reminiscent of Cu(4)-L(6) (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).
Chen
Xiaohua
X
Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
Hua
Haiqing
H
Balamurugan
Kuppusamy
K
Kong
Xiangming
X
Zhang
Limei
L
George
Graham N
GN
Georgiev
Oleg
O
Schaffner
Walter
W
Giedroc
David P
DP
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D003300:Copper / Q000737:chemistry / Q000633:toxicity*; D003545:Cysteine / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000187:drug effects; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014965:X-Rays; D000097809:Transcription Factor MTF-1
D003300:Copper; D003545:Cysteine; D004268:DNA-Binding Proteins; D013455:Sulfur; D014157:Transcription Factors; D000097809:Transcription Factor MTF-1