Format

Send to

Choose Destination
Biophys J. 2015 Jul 21;109(2):277-86. doi: 10.1016/j.bpj.2015.06.014.

MD simulations and FRET reveal an environment-sensitive conformational plasticity of importin-β.

Author information

1
Free Floater (Junior) Research Group "Applied Synthetic Biology", Institute for Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
2
Department of Theoretical and Computational Biophysics, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany.
3
Third Institute of Physics-Biophysics, Georg-August University Göttingen, Göttingen, Germany.
4
Institute for Microbiology and Genetics, Department of Molecular Structural Biology, Georg-August University Göttingen, Göttingen, Germany.
5
Department of Molecular Biology, Faculty of Medicine, Georg-August University Göttingen, Göttingen, Germany.
6
Department of Theoretical and Computational Biophysics, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany. Electronic address: hgrubmu@gwdg.de.
7
Free Floater (Junior) Research Group "Applied Synthetic Biology", Institute for Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany. Electronic address: hneumann@uni-goettingen.de.

Abstract

The nuclear pore complex mediates nucleocytoplasmic transport of macromolecules in eukaryotic cells. Transport through the pore is restricted by a hydrophobic selectivity filter comprising disordered phenylalanine-glycine-rich repeats of nuclear pore proteins. Exchange through the pore requires specialized transport receptors, called exportins and importins, that interact with cargo proteins in a RanGTP-dependent manner. These receptors are highly flexible superhelical structures composed of HEAT-repeat motifs that adopt various degrees of extension in crystal structures. Here, we performed molecular-dynamics simulations using crystal structures of Importin-β in its free form or in complex with nuclear localization signal peptides as the starting conformation. Our simulations predicted that initially compact structures would adopt extended conformations in hydrophilic buffers, while contracted conformations would dominate in more hydrophobic solutions, mimicking the environment of the nuclear pore. We confirmed this experimentally by Förster resonance energy transfer experiments using dual-fluorophore-labeled Importin-β. These observations explain seemingly contradictory crystal structures and suggest a possible mechanism for cargo protection during passage of the nuclear pore. Such hydrophobic switching may be a general principle for environmental control of protein function.

PMID:
26200863
PMCID:
PMC4621615
DOI:
10.1016/j.bpj.2015.06.014
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center