3CN5

Crystal structure of the Spinach Aquaporin SoPIP2;1 S115E, S274E mutant

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.181 
  • R-Value Work: 0.159 
  • R-Value Observed: 0.160 

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This is version 1.1 of the entry. See complete history. 


Literature

Structural and functional analysis of SoPIP2;1 mutants adds insight into plant aquaporin gating.

Nyblom, M., Frick, A., Wang, Y., Ekvall, M., Hallgren, K., Hedfalk, K., Neutze, R., Tajkhorshid, E., Tornroth-Horsefield, S.

(2009) J Mol Biol 387: 653-668

  • DOI: 10.1016/j.jmb.2009.01.065
  • Primary Citation of Related Structures:  
    3CLL, 3CN6, 3CN5

  • PubMed Abstract: 

    • Plant plasma membrane aquaporins facilitate water flux into and out of plant cells, thus coupling their cellular function to basic aspects of plant physiology. Posttranslational modifications of conserved phosphorylation sites, changes in cytoplasmic pH and the binding of Ca(2+) can regulate water transport activity by gating the plasma membrane aquaporins ...

    Plant plasma membrane aquaporins facilitate water flux into and out of plant cells, thus coupling their cellular function to basic aspects of plant physiology. Posttranslational modifications of conserved phosphorylation sites, changes in cytoplasmic pH and the binding of Ca(2+) can regulate water transport activity by gating the plasma membrane aquaporins. A structural mechanism unifying these diverse biochemical signals has emerged for the spinach aquaporin SoPIP2;1, although several questions concerning the opening mechanism remain. Here, we describe the X-ray structures of the S115E and S274E single SoPIP2;1 mutants and the corresponding double mutant. Phosphorylation of these serines is believed to increase water transport activity of SoPIP2;1 by opening the channel. However, all mutants crystallised in a closed conformation, as confirmed by water transport assays, implying that neither substitution fully mimics the phosphorylated state. Nevertheless, a half-turn extension of transmembrane helix 1 occurs upon the substitution of Ser115, which draws the C(alpha) atom of Glu31 10 A away from its wild-type conformation, thereby disrupting the divalent cation binding site involved in the gating mechanism. Mutation of Ser274 disorders the C-terminus but no other significant conformational changes are observed. Inspection of the hydrogen-bond interactions within loop D suggested that the phosphorylation of Ser188 may also produce an open channel, and this was supported by an increased water transport activity for the S188E mutant and molecular dynamics simulations. These findings add additional insight into the general mechanism of plant aquaporin gating.

    Organizational Affiliation: 

    Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.



Macromolecules
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(by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
AquaporinA304Spinacia oleraceaMutation(s): 2 
Gene Names: SOVF_195660
Membrane protein
Mpstruc		Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL		Sub Group: 
Channels: Aquaporins and Glyceroporins		Protein: 
PIP2;1 plant aquaporin, S115E mutant
Find proteins for Q41372 (Spinacia oleracea)
Explore Q41372 
Go to UniProtKB:  Q41372
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.05 Å
  • R-Value Free: 0.181 
  • R-Value Work: 0.159 
  • R-Value Observed: 0.160 
  • Space Group: I 4
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 87.033α = 90
b = 87.033β = 90
c = 87.392γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
MOSFLMdata reduction
SCALAdata scaling
MOLREPphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-02-24
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance