Structural Insights into the Nucleotide-Binding Domains of the P1B-type ATPases HMA6 and HMA8 from Arabidopsis thaliana

PLoS One. 2016 Nov 1;11(11):e0165666. doi: 10.1371/journal.pone.0165666. eCollection 2016.

Abstract

Copper is a crucial ion in cells, but needs to be closely controlled due to its toxic potential and ability to catalyse the formation of radicals. In chloroplasts, an important step for the proper functioning of the photosynthetic electron transfer chain is the delivery of copper to plastocyanin in the thylakoid lumen. The main route for copper transport to the thylakoid lumen is driven by two PIB-type ATPases, Heavy Metal ATPase 6 (HMA6) and HMA8, located in the inner membrane of the chloroplast envelope and in the thylakoid membrane, respectively. Here, the crystal structures of the nucleotide binding domain of HMA6 and HMA8 from Arabidopsis thaliana are reported at 1.5Å and 1.75Å resolution, respectively, providing the first structural information on plants Cu+-ATPases. The structures reveal a compact domain, with two short helices on both sides of a twisted beta-sheet. A double mutant, aiding in the crystallization, provides a new crystal contact, but also avoids an internal clash highlighting the benefits of construct modifications. Finally, the histidine in the HP motif of the isolated domains, unable to bind ATP, shows a side chain conformation distinct from nucleotide bound structures.

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / metabolism
  • Amino Acid Sequence
  • Arabidopsis / chemistry*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / chemistry*
  • Arabidopsis Proteins / metabolism
  • Binding Sites
  • Copper / metabolism
  • Crystallography, X-Ray
  • Models, Molecular
  • Nucleotides / metabolism*
  • Protein Binding
  • Protein Domains
  • Sequence Alignment

Substances

  • Arabidopsis Proteins
  • HMA8 protein, Arabidopsis
  • Nucleotides
  • Copper
  • Adenosine Triphosphatases
  • HMA6 protein, Arabidopsis

Grants and funding

HM was supported by two post-doc fellowships, first from the European Community’s Seventh Framework Programme FP7/2007–2013 under grant agreement no. HEALTH- F4-2007-201924, EDICT Consortium and then from the Grenoble Alliance for Integrated Structural Cell Biology GRAL (ANR-10-LABX-49-01). EPP was supported by the Institut Universitaire de France. SR was supported by a chair from the French Centre National de la Recherche Scientifique and from the University Grenoble Alpes. These funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.