Structure and transport mechanism of the sodium/proton antiporter MjNhaP1

Cristina Batista Paulino, David Woehlert, Ekatarina Karpotova, Özkan Yildiz, Werner Kuehlbrandt

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Abstract

Sodium/proton antiporters are essential for sodium and pH homeostasis and play a major role in human health and disease. We determined the structures of the archaeal sodium/proton antiporter MjNhaP1 in two complementary states. The inward-open state was obtained by x-ray crystallography in the presence of sodium at pH8, where the transporter is highly active. The outward-open state was obtained by electron crystallography without sodium at pH4, where MjNhaP1 is inactive. Comparison of both structures reveals a 7 degrees tilt of the 6-helix bundle. Na-22(+) uptake measurements indicate non-cooperative transport with an activity maximum at pH7.5. We conclude that binding of a Na+ ion from the outside induces helix movements that close the extracellular cavity, open the cytoplasmic funnel, and result in a similar to 5 angstrom vertical relocation of the ion binding site to release the substrate ion into the cytoplasm.
Original languageEnglish
Article numbere03583
Pages (from-to)1-21
Number of pages21
JournaleLife
Volume3
DOIs
Publication statusPublished - 26-Nov-2014
Externally publishedYes

Keywords

  • Structure
  • transport
  • MjNhaP1 antiporter
  • cryo-EM
  • single particle analysis

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