Crystal structure of Arabidopsis importin-alpha3 armadillo repeat domain

Experimental Data Snapshot

  • Resolution: 2.90 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.221 

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This is version 1.6 of the entry. See complete history


Probing formation of cargo/importin-alpha transport complexes in plant cells using a pathogen effector.

Wirthmueller, L.Roth, C.Fabro, G.Caillaud, M.C.Rallapalli, G.Asai, S.Sklenar, J.Jones, A.M.Wiermer, M.Jones, J.D.Banfield, M.J.

(2015) Plant J 81: 40-52

  • DOI: https://doi.org/10.1111/tpj.12691
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Importin-αs are essential adapter proteins that recruit cytoplasmic proteins destined for active nuclear import to the nuclear transport machinery. Cargo proteins interact with the importin-α armadillo repeat domain via nuclear localization sequences (NLSs), short amino acids motifs enriched in Lys and Arg residues. Plant genomes typically encode several importin-α paralogs that can have both specific and partially redundant functions. Although some cargos are preferentially imported by a distinct importin-α it remains unknown how this specificity is generated and to what extent cargos compete for binding to nuclear transport receptors. Here we report that the effector protein HaRxL106 from the oomycete pathogen Hyaloperonospora arabidopsidis co-opts the host cell's nuclear import machinery. We use HaRxL106 as a probe to determine redundant and specific functions of importin-α paralogs from Arabidopsis thaliana. A crystal structure of the importin-α3/MOS6 armadillo repeat domain suggests that five of the six Arabidopsis importin-αs expressed in rosette leaves have an almost identical NLS-binding site. Comparison of the importin-α binding affinities of HaRxL106 and other cargos in vitro and in plant cells suggests that relatively small affinity differences in vitro affect the rate of transport complex formation in vivo. Our results suggest that cargo affinity for importin-α, sequence variation at the importin-α NLS-binding sites and tissue-specific expression levels of importin-αs determine formation of cargo/importin-α transport complexes in plant cells.

  • Organizational Affiliation

    The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK; Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Importin subunit alpha531Arabidopsis thalianaMutation(s): 0 
Gene Names: MOS6At4g02150
Find proteins for O04294 (Arabidopsis thaliana)
Explore O04294 
Go to UniProtKB:  O04294
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO04294
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.90 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.221 
  • Space Group: H 3
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 127.518α = 90
b = 127.518β = 90
c = 89.782γ = 120
Software Package:
Software NamePurpose
iMOSFLMdata reduction
PDB_EXTRACTdata extraction

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Biotechnology and Biological Sciences Research Council (BBSRC)United KingdomBBJ00453
Biotechnology and Biological Sciences Research Council (BBSRC)United KingdomBBK009176

Revision History  (Full details and data files)

  • Version 1.0: 2014-10-08
    Type: Initial release
  • Version 1.1: 2014-10-22
    Changes: Database references
  • Version 1.2: 2015-01-14
    Changes: Database references
  • Version 1.3: 2015-02-04
    Changes: Derived calculations, Other
  • Version 1.4: 2017-09-20
    Changes: Author supporting evidence, Data collection, Database references, Derived calculations, Other, Source and taxonomy, Structure summary
  • Version 1.5: 2020-01-01
    Changes: Author supporting evidence
  • Version 1.6: 2023-12-27
    Changes: Data collection, Database references, Refinement description