5EKF: Crystallization And X-ray Diffraction Data Collection Of Importin- Alpha From Mus Musculus Complexed With A Xpg Nls Peptide, Fragment 1

Xeroderma pigmentosum type G (XPG) proteins are involved in DNA lesion recognition and promotion of nucleotide excision repair. Specific mutations in these proteins may lead to Cockayne syndrome, in which the patients may display severe developmental retardation and neurological abnormalities. No structural information is available for their spacer region or the C-terminal domain, which are important, respectively, for specific nucleotide excision repair activity and substrate specificity, as well as nuclear translocation. Immunofluorescence studies suggested two specific regions of the XPG C-terminus as potential bipartite nuclear localization sequences, which would be responsible for its translocation to the nucleus by the classical nuclear import pathway mediated by the importin-alpha (Impalpha). Thus, in order to test these hypotheses and gain insight into the structural basis for the nuclear import process for the XPG protein, we solved the crystal structures of complexes formed by the Impalpha and peptides corresponding to both putative nuclear localization signal (NLS) sequences (XPG1 and XPG2) and performed isothermal titration calorimetry assays to determine their binding affinities. Structural experiments confirm the binding of both NLS peptides to Impalpha but, unexpectedly, they bind to the receptor as monopartite NLSs. The isothermal titration calorimetry assays demonstrated that XPG1 and XPG2 peptides bind to two separate binding sites, but with high affinity to the major NLS-binding site of the Impalpha, resembling classical monopartite SV40 TAg NLS. The results lead to insights about what distinguishes monopartite and bipartite NLSs, as well as the differential roles of XPG1 and XPG2 NLSs in the nuclear localization of XPG.
PDB ID: 5EKFDownload
MMDB ID: 136419
PDB Deposition Date: 2015/11/3
Updated in MMDB: 2016/06
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Mus musculus
Similar Structures:
Biological Unit for 5EKF: trimeric; determined by author and by software (PISA)
Molecular Components in 5EKF
Label Count Molecule
Proteins (3 molecules)
DNA Repair Protein Complementing Xp-g Cells(Gene symbol: ERCC5)
Molecule annotation
Importin Subunit Alpha-1(Gene symbol: Kpna2)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB