Crystal structure of AqpZ H174G,T183F

Experimental Data Snapshot

  • Resolution: 2.50 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.186 
  • R-Value Observed: 0.188 

Starting Model: experimental
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This is version 1.5 of the entry. See complete history


Structural context shapes the aquaporin selectivity filter.

Savage, D.F.O'Connell, J.D.Miercke, L.J.Finer-Moore, J.Stroud, R.M.

(2010) Proc Natl Acad Sci U S A 107: 17164-17169

  • DOI: https://doi.org/10.1073/pnas.1009864107
  • Primary Citation of Related Structures:  
    3NK5, 3NKA, 3NKC

  • PubMed Abstract: 

    Aquaporins are transmembrane channels that facilitate the permeation of water and small, uncharged amphipathic molecules across cellular membranes. One distinct aquaporin subfamily contains pure water channels, whereas a second subfamily contains channels that conduct small alditols such as glycerol, in addition to water. Distinction between these substrates is central to aquaporin function, though the contributions of protein structural motifs required for selectivity are not yet fully characterized. To address this question, we sequentially engineered three signature amino acids of the glycerol-conducting subfamily into the Escherichia coli water channel aquaporin Z (AqpZ). Functional analysis of these mutant channels showed a decrease in water permeability but not the expected increase in glycerol conduction. Using X-ray crystallography, we determined the atomic resolution structures of the mutant channels. The structures revealed a channel surprisingly similar in size to the wild-type AqpZ pore. Comparison with measured rates of transport showed that, as the size of the selectivity filter region of the channel approaches that of water, channel hydrophilicity dominated water conduction energetics. In contrast, the major determinant of selectivity for larger amphipathic molecules such as glycerol was channel cross-section size. Finally, we find that, although the selectivity filter region is indeed central to substrate transport, other structural elements that do not directly interact with the substrates, such as the loop connecting helices M6 and M7, and the C loop between helices C4 and C5, play an essential role in facilitating selectivity.

  • Organizational Affiliation

    Graduate Group in Biophysics, Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158-2517, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Aquaporin Z
A, B
234Escherichia coli K-12Mutation(s): 2 
Gene Names: aqpZb0875bniPJW0859
Membrane Entity: Yes 
Find proteins for P60844 (Escherichia coli (strain K12))
Explore P60844 
Go to UniProtKB:  P60844
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP60844
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.50 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.186 
  • R-Value Observed: 0.188 
  • Space Group: P 4
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 92.784α = 90
b = 92.784β = 90
c = 78.919γ = 90
Software Package:
Software NamePurpose
SCALAdata scaling
PDB_EXTRACTdata extraction
MOSFLMdata reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2010-11-03
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2012-09-05
    Changes: Derived calculations
  • Version 1.3: 2017-11-08
    Changes: Refinement description
  • Version 1.4: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Database references, Derived calculations, Structure summary
  • Version 1.5: 2023-09-06
    Changes: Data collection, Database references, Refinement description, Structure summary