4XRK: Crystal Structure of Importin Beta in a Polyethylene Glycol Condition

In eukaryotic cells, the exchange of macromolecules between the nucleus and cytoplasm is highly selective and requires specialized soluble transport factors. Many of them belong to the importin-beta superfamily, the members of which share an overall superhelical structure owing to the tandem arrangement of a specific motif, the HEAT repeat. This structural organization leads to great intrinsic flexibility, which in turn is a prerequisite for the interaction with a variety of proteins and for its transport function. During the passage from the aqueous cytosol into the nucleus, the receptor passes the gated channel of the nuclear pore complex filled with a protein meshwork of unknown organization, which seems to be highly selective owing to the presence of FG-repeats, which are peptides with hydrophobic patches. Here, the structural changes of free importin-beta from a single organism, crystallized in polar (salt) or apolar (PEG) buffer conditions, are reported. This allowed analysis of the structural changes, which are attributable to the surrounding milieu and are not affected by bound interaction partners. The importin-beta structures obtained exhibit significant conformational changes and suggest an influence of the polarity of the environment, resulting in an extended conformation in the PEG condition. The significance of this observation is supported by SAXS experiments and the analysis of other crystal structures of importin-beta deposited in the Protein Data Bank.
PDB ID: 4XRKDownload
MMDB ID: 135944
PDB Deposition Date: 2015/1/21
Updated in MMDB: 2016/07
Experimental Method:
x-ray diffraction
Resolution: 3.25  Å
Source Organism:
Similar Structures:
Biological Unit for 4XRK: monomeric; determined by author and by software (PISA)
Molecular Components in 4XRK
Label Count Molecule
Protein (1 molecule)
Importin Beta
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB