1iq1
From Proteopedia
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CRYSTAL STRUCTURE OF THE IMPORTIN-ALPHA(44-54)-IMPORTIN-ALPHA(70-529) COMPLEX
Overview
Proteins containing the classical nuclear localization sequences (NLSs), are imported into the nucleus by the importin-alpha/beta heterodimer., Importin-alpha contains the NLS binding site, whereas importin-beta, mediates the translocation through the nuclear pore. We characterized the, interactions involving importin-alpha during nuclear import using a, combination of biophysical techniques (biosensor, crystallography, sedimentation equilibrium, electrophoresis, and circular dichroism)., Importin-alpha is shown to exist in a monomeric autoinhibited state, (association with NLSs undetectable by biosensor). Association with, importin-beta (stoichiometry, 1:1; K(D) = 1.1 x 10(-8) m) increases the, affinity for NLSs; the importin-alpha/beta complex binds representative, monopartite NLS (simian virus 40 large T-antigen) and bipartite NLS, (nucleoplasmin) with affinities (K(D) = 3.5 x 10(-8) m and 4.8 x 10(-8) m, respectively) comparable with those of a truncated importin-alpha lacking, the autoinhibitory domain (T-antigen NLS, K(D) = 1.7 x 10(-8) m;, nucleoplasmin NLS, K(D) = 1.4 x 10(-8) m). The autoinhibitory domain (as a, separate peptide) binds the truncated importin-alpha, and the crystal, structure of the complex resembles the structure of full-length, importin-alpha. Our results support the model of regulation of nuclear, import mediated by the intrasteric autoregulatory sequence of, importin-alpha and provide a quantitative description of the binding and, regulatory steps during nuclear import.
About this Structure
1IQ1 is a Protein complex structure of sequences from Mus musculus. Full crystallographic information is available from OCA.
Reference
Biophysical characterization of interactions involving importin-alpha during nuclear import., Catimel B, Teh T, Fontes MR, Jennings IG, Jans DA, Howlett GJ, Nice EC, Kobe B, J Biol Chem. 2001 Sep 7;276(36):34189-98. Epub 2001 Jul 11. PMID:11448961
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