Structure of the archaeal Na+/H+ antiporter NhaP1 and functional role of transmembrane helix 1

Panchali Goswami, Cristina Batista Paulino, Dilem Hizlan, Janet Vonck, Özkan Yildiz, Werner Kuehlbrandt

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We have determined the structure of the archaeal sodium/proton antiporter NhaP1 at 7 angstrom resolution by electron crystallography of 2D crystals. NhaP1 is a dimer in the membrane, with 13 membrane-spanning a-helices per protomer, whereas the distantly related bacterial NhaA has 12. Dimer contacts in the two antiporters are very different, but the structure of a six-helix bundle at the tip of the protomer is conserved. The six-helix bundle of NhaA contains two partially unwound alpha-helices thought to harbour the ion-translocation site, which is thus similar in NhaP1. A model of NhaP1 based on detailed sequence comparison and the NhaA structure was fitted to the 7 angstrom map. The additional N-terminal helix 1 of NhaP1, which appears to be an uncleaved signal sequence, is located near the dimer interface. Similar sequences are present in many eukaryotic homologues of NhaP1, including NHE1. Although fully folded and able to dimerize, NhaP1 constructs without helix 1 are inactive. Possible reasons are investigated and discussed. The EMBO Journal (2011) 30, 439-449. doi:10.1038/emboj.2010.321; Published online 10 December 2010
Original languageEnglish
Pages (from-to)439-449
Number of pages10
JournalThe EMBO Journal
Publication statusPublished - 19-Jan-2011
Externally publishedYes


  • electron microscopy
  • membrane protein structure
  • membrane transport
  • molecular model
  • monovalent cation/proton antiporters

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