| 1. |
- Kahra, Dana, et al.
(författare)
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Human Copper Chaperone Atox1 Translocates to the Nucleus but does not Bind DNA In Vitro.
- 2015
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Ingår i: Protein and peptide letters. - : Bentham Science. - 1875-5305 .- 0929-8665. ; 22:6, s. 532-8
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Tidskriftsartikel (refereegranskat)abstract
- After Ctr1-mediated cell uptake, copper (Cu) is transported by the cytoplasmic Cu chaperone Atox1 to P1B type ATPases ATP7A and ATP7B in the Golgi network, for incorporation into Cudependent enzymes. Atox1 is a small 68-residue protein that binds Cu in a conserved CXXC motif; it delivers Cu to target domains in ATP7A/B via direct protein-protein interactions. Specific transcription factors regulating expression of the human Cu transport proteins have not been reported although Atox1 was recently suggested to have dual functionality such that it, in addition to its cytoplasmic chaperone function, acts as a transcription factor in the nucleus. To examine this hypothesis, here we investigated the localization of Atox1 in HeLa cells using fluorescence imaging in combination with in vitro binding experiments to fluorescently labeled DNA duplexes harboring the proposed promotor sequence. We found that whereas Atox1 is present in the nucleus in HeLa cells, it does not bind to DNA in vitro. It appears that Atox1 mediates transcriptional regulation via additional (unknown) proteins.
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| 2. |
- Mondol, Tanumoy, et al.
(författare)
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Copper binding triggers compaction in N-terminal tail of human copper pump ATP7B
- 2016
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 470:3, s. 663-669
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Tidskriftsartikel (refereegranskat)abstract
- Protein conformational changes are fundamental to biological reactions. For copper ion transport, the multi-domain protein ATP7B in the Golgi network receives copper from the cytoplasmic copper chaperone Atox1 and, with energy from ATP hydrolysis, moves the metal to the lumen for loading of copper dependent enzymes. Although anticipated, conformational changes involved in ATP7B's functional cycle remain elusive. Using spectroscopic methods we here demonstrate that the four most N-terminal metal binding domains in ATP7B, upon stoichiometric copper addition, adopt a more compact arrangement which has a higher thermal stability than in the absence of copper. In contrast to previous reports, no stable complex was found in solution between the metal-binding domains and the nucleotide-binding domain of ATP7B. Metal-dependent movement of the first four metal-binding domains in ATP7B may be a trigger that initiates the overall catalytic cycle.
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