3oqs
From Proteopedia
Crystal structure of importin-alpha bound to a CLIC4 NLS peptide
Structural highlights
FunctionCLIC4_HUMAN Can insert into membranes and form poorly selective ion channels that may also transport chloride ions. Channel activity depends on the pH. Membrane insertion seems to be redox-regulated and may occur only under oxydizing conditions. Promotes cell-surface expression of HRH3. Has alternate cellular functions like a potential role in angiogenesis or in maintaining apical-basolateral membrane polarity during mitosis and cytokinesis. Could also promote endothelial cell proliferation and regulate endothelial morphogenesis (tubulogenesis).[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedIt has been reported that a human chloride intracellular channel (CLIC) protein, CLIC4, translocates to the nucleus in response to cellular stress, facilitated by a putative CLIC4 nuclear localization signal (NLS). The CLIC4 NLS adopts an alpha-helical structure in the native CLIC4 fold. It is proposed that CLIC4 is transported to the nucleus via the classical nuclear import pathway after binding the import receptor, importin-alpha. In this study, we have determined the X-ray crystal structure of a truncated form of importin-alpha lacking the importin-beta binding domain, bound to a CLIC4 NLS peptide. The NLS peptide binds to the major binding site in an extended conformation similar to that observed for the classical simian virus 40 large T-antigen NLS. A Tyr residue within the CLIC4 NLS makes surprisingly favourable interactions by forming side-chain hydrogen bonds to the importin-alpha backbone. This structural evidence supports the hypothesis that CLIC4 translocation to the nucleus is governed by the importin-alpha nuclear import pathway, provided that CLIC4 can undergo a conformational rearrangement that exposes the NLS in an extended conformation. Crystal structure of importin-alpha bound to a peptide bearing the nuclear localisation signal from chloride intracellular channel protein 4.,Mynott AV, Harrop SJ, Brown LJ, Breit SN, Kobe B, Curmi PM FEBS J. 2011 May;278(10):1662-75. doi: 10.1111/j.1742-4658.2011.08086.x., Epub 2011 Mar 30. PMID:21388519[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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