Human copper transporter ATP7B (Wilson disease protein) forms stable dimers in vitro and in cells

J Biol Chem. 2017 Nov 17;292(46):18760-18774. doi: 10.1074/jbc.M117.807263. Epub 2017 Aug 24.

Abstract

ATP7B is a copper-transporting P1B-type ATPase (Cu-ATPase) with an essential role in human physiology. Mutations in ATP7B cause the potentially fatal Wilson disease, and changes in ATP7B expression are observed in several cancers. Despite its physiologic importance, the biochemical information about ATP7B remains limited because of a complex multidomain organization of the protein. By analogy with the better characterized prokaryotic Cu-ATPases, ATP7B is assumed to be a single-chain monomer. We show that in eukaryotic cells, human ATP7B forms dimers that can be purified following solubilization. Deletion of the four N-terminal metal-binding domains, characteristic for human ATP7B, does not disrupt dimerization, i.e. the dimer interface is formed by the domains that are conserved among Cu-ATPases. Unlike the full-length ATP7B, which is targeted to the trans-Golgi network, 1-4ΔMBD-7B is targeted primarily to vesicles. This result and the analysis of differentially tagged ATP7B variants indicate that the dimeric structure is retained during ATP7B trafficking between the intracellular compartments. Purified dimeric species of 1-4ΔMBD-7B were characterized by a negative stain electron microscopy in the presence of ADP/MgCl2 Single-particle analysis yielded a low-resolution 3D model that provides the first insight into an overall architecture of a human Cu-ATPase, positions of the main domains, and a dimer interface.

Keywords: ATPase; calcium ATPase; copper transport; dimerization; membrane transport.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Copper / metabolism
  • Copper-Transporting ATPases / chemistry*
  • Copper-Transporting ATPases / genetics
  • Copper-Transporting ATPases / metabolism*
  • Crystallography, X-Ray
  • HEK293 Cells
  • Hepatolenticular Degeneration / genetics
  • Hepatolenticular Degeneration / metabolism
  • Humans
  • Models, Molecular
  • Mutation
  • Protein Binding
  • Protein Conformation
  • Protein Domains
  • Protein Multimerization*
  • Protein Stability
  • Protein Transport

Substances

  • Copper
  • ATP7B protein, human
  • Copper-Transporting ATPases

Associated data

  • PDB/3EW9