Ammonia permeable aquaporin AtTIP2;1

Experimental Data Snapshot

  • Resolution: 1.18 Å
  • R-Value Free: 0.115 
  • R-Value Work: 0.104 
  • R-Value Observed: 0.104 

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Crystal Structure of an Ammonia-Permeable Aquaporin.

Kirscht, A.Kaptan, S.S.Bienert, G.P.Chaumont, F.Nissen, P.de Groot, B.L.Kjellbom, P.Gourdon, P.Johanson, U.

(2016) PLoS Biol 14: e1002411-e1002411

  • DOI: https://doi.org/10.1371/journal.pbio.1002411
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Aquaporins of the TIP subfamily (Tonoplast Intrinsic Proteins) have been suggested to facilitate permeation of water and ammonia across the vacuolar membrane of plants, allowing the vacuole to efficiently sequester ammonium ions and counteract cytosolic fluctuations of ammonia. Here, we report the structure determined at 1.18 Å resolution from twinned crystals of Arabidopsis thaliana aquaporin AtTIP2;1 and confirm water and ammonia permeability of the purified protein reconstituted in proteoliposomes as further substantiated by molecular dynamics simulations. The structure of AtTIP2;1 reveals an extended selectivity filter with the conserved arginine of the filter adopting a unique unpredicted position. The relatively wide pore and the polar nature of the selectivity filter clarify the ammonia permeability. By mutational studies, we show that the identified determinants in the extended selectivity filter region are sufficient to convert a strictly water-specific human aquaporin into an AtTIP2;1-like ammonia channel. A flexible histidine and a novel water-filled side pore are speculated to deprotonate ammonium ions, thereby possibly increasing permeation of ammonia. The molecular understanding of how aquaporins facilitate ammonia flux across membranes could potentially be used to modulate ammonia losses over the plasma membrane to the atmosphere, e.g., during photorespiration, and thereby to modify the nitrogen use efficiency of plants.

  • Organizational Affiliation

    Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, Lund, Sweden.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Aquaporin TIP2-1275Arabidopsis thalianaMutation(s): 0 
Gene Names: TIP2-1At3g16240MYA6.10
Membrane Entity: Yes 
Find proteins for Q41951 (Arabidopsis thaliana)
Explore Q41951 
Go to UniProtKB:  Q41951
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ41951
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.18 Å
  • R-Value Free: 0.115 
  • R-Value Work: 0.104 
  • R-Value Observed: 0.104 
  • Space Group: I 4
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 89.27α = 90
b = 89.27β = 90
c = 82.491γ = 90
Software Package:
Software NamePurpose
SCALAdata scaling
PDB_EXTRACTdata extraction
XDSdata reduction

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Swedish Research CouncilSweden--
(Biomemos) of the European Research Council--
Danscatt program of the Danish Council of Independent ResearchDenmark--
Formas, the Research School of Pharmaceutical Sciences FLAEKSweden--

Revision History  (Full details and data files)

  • Version 1.0: 2016-04-06
    Type: Initial release
  • Version 1.1: 2024-01-10
    Changes: Data collection, Database references, Refinement description