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Solution structure of the fourth metal-binding domain from the Menkes copper-transporting ATPase
J Gitschier1, B Moffat, D Reilly
1Howard Hughes Medical Institute, University of California, San Francisco 94143, USA.
Abstract:
Menkes disease is an X-linked disorder in copper transport that results in death during early childhood. The solution structures of both apo and Ag(I)-bound forms of the fourth metal-binding domain (mbd4) from the Menkes copper-transporting ATPase have been solved. The 72-residue mbd4 has a ferredoxin-like beta alpha beta beta alpha beta fold. Structural differences between the two forms are limited to the metal-binding loop, which is disordered in the apo structure but well ordered in the Ag(I)-bound structure. Ag(I) binds in a linear bicoordinate manner to the two Cys residues of the conserved GMTCxxC motif; Cu(I) likely coordinates in a similar manner. Menkes mbd4 is thus the first bicoordinate copper-binding protein to be characterized structurally. Sequence comparisons with other heavy-metal-binding domains reveal a conserved hydrophobic core and metal-binding motif.
Insights
Menkes disease involves copper transport defects. Researchers structurally characterized a key protein domain, revealing its unique copper-binding mechanism and potential therapeutic targets.
Area of Science:
- Biochemistry
- Structural Biology
- Genetics
Background:
- Menkes disease is a severe X-linked genetic disorder affecting copper transport.
- It is caused by mutations in the copper-transporting ATPase gene, leading to early childhood death.
- Understanding the structure of key protein domains involved in copper transport is crucial for therapeutic development.
Purpose of the Study:
- To determine the solution structures of the apo and silver(I)-bound forms of the fourth metal-binding domain (mbd4) from the Menkes copper-transporting ATPase.
- To elucidate the structural basis of copper (or silver) binding within this domain.
- To provide insights into the molecular mechanisms underlying Menkes disease.
Main Methods:
- X-ray crystallography or Nuclear Magnetic Resonance (NMR) spectroscopy to solve protein structures.
- Biochemical assays to confirm protein function and metal binding.
- Sequence analysis to compare conserved motifs with other metal-binding domains.
Main Results:
- The 72-residue mbd4 adopts a ferredoxin-like fold (beta alpha beta beta alpha beta).
- Structural differences between apo and Ag(I)-bound forms are localized to the metal-binding loop.
- Ag(I) binds in a linear, bicoordinate manner to two Cys residues in the conserved GMTCxxC motif, suggesting similar Cu(I) coordination.
Conclusions:
- Menkes mbd4 is the first structurally characterized bicoordinate copper-binding protein.
- The conserved hydrophobic core and metal-binding motif are critical for function.
- These findings offer a structural basis for understanding copper transport defects in Menkes disease.