title: Copper transfer to the N-terminal domain of the Wilson disease protein (ATP7B): X-ray absorption spectroscopy of reconstituted and chaperone-loaded metal binding domains and their interaction with exogenous ligands.
abstract: The copper-transporting ATPases are 165-175 kDa membrane proteins, composed of 8 transmembrane segments and two large cytosolic domains, the N-terminal copper-binding domain and the catalytic ATP-hydrolyzing domain. In ATP7B, the Wilson disease protein, the N-terminal domain is made up of six metal-binding sub-domains containing the MXCXXC motif which is known to coordinate copper via the two cysteine residues. We have expressed the N-terminal domain of ATP7B as a soluble C-terminal fusion with the maltose binding protein. This expression system produces a protein which can be reconstituted with copper without recourse to the harsh denaturing conditions or low pH reported by other laboratories. Here we describe the reconstitution of the metal binding domains (MBD) with Cu(I) using a number of different protocols, including copper loading via the chaperone, Atox1. X-ray absorption spectra have been obtained on all these derivatives, and their ability to bind exogenous ligands has been assessed. The results establish that the metal-binding domains bind Cu(I) predominantly in a bis cysteinate environment, and are able to bind exogenous ligands such as DTT in a similar fashion to Atox1. We have further observed that exogenous ligand binding induces the formation of a Cu-Cu interaction which may signal a conformational change of the N-terminal domain.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health and Sciences University, Portland, OR 97239, USA.
authors.forename: Martina
authors.initials: M
authors.lastname: Ralle
authors.forename: Svetlana
authors.initials: S
authors.lastname: Lutsenko
authors.forename: Ninian J
authors.initials: NJ
authors.lastname: Blackburn
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D000079922:Copper Transport Proteins; D000073840:Copper-Transporting ATPases; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D058619:Maltose-Binding Proteins; D056511:Metallochaperones; D018832:Molecular Chaperones / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: C474500:ATOX1 protein, human; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; D008024:Ligands; D058619:Maltose-Binding Proteins; D056511:Metallochaperones; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; D003300:Copper; D000251:Adenosine Triphosphatases; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases