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RanBP1 stabilizes the interaction of Ran with p97 nuclear protein import.

http://www.ncbi.nlm.nih.gov/pubmed/8909533

Three factors have been identified that reconstitute nuclear protein import in a permeabilized cell assay: the NLS receptor, p97, and Ran/TC4. Ran/TC4, in turn, interacts with a number of proteins that are involved in the regulation of GTP hydrolysis or are components of the nuclear pore. Two Ran-binding proteins, RanBP1 and RanBP2, form discrete complexes with p97 as demonstrated by immunoadsorption from HeLa cell extracts fractionated by gel filtration chromatography. A > 400-kD complex contains p97, Ran, and RanBP2. Another complex of 150-300 kD was comprised of p97, Ran, and RanBP1. This second trimeric complex could be reconstituted from recombinant proteins. In solution binding assays, Ran-GTP bound p97 with high affinity, but the binding of Ran-GDP to p97 was undetectable. The addition of RanBP1 with Ran-GDP or Ran-GTP increased the affinity of both forms of Ran for p97 to the same level. Binding of Ran-GTP to p97 dissociated p97 from immobilized NLS receptor while the Ran-GDP/RanBP1/p97 complex did not dissociate from the receptor. In a digitonin-permeabilized cell docking assay, RanBP1 stabilizes the receptor complex against temperature-dependent release from the pore. When added to an import assay with recombinant NLS receptor, p97 and Ran-GDP, RanBP1 significantly stimulates transport. These results suggest that RanBP1 promotes both the docking and translocation steps in nuclear protein import by stabilizing the interaction of Ran-GDP with p97.

Pubmed ID: 8909533 RIS Download

Mesh terms: Biological Transport | Cell Membrane Permeability | Cell Nucleus | DNA-Binding Proteins | Digitonin | GTP-Binding Proteins | Guanosine Diphosphate | Guanosine Triphosphate | HeLa Cells | Humans | Macromolecular Substances | Molecular Chaperones | Nuclear Envelope | Nuclear Pore Complex Proteins | Nuclear Proteins | Protein Binding | Recombinant Fusion Proteins | alpha Karyopherins | beta Karyopherins | ran GTP-Binding Protein

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Associated grants

  • Agency: NCI NIH HHS, Id: 5-T32 CA 09560
  • Agency: NIGMS NIH HHS, Id: 5-T32-GM08152-10
  • Agency: NIGMS NIH HHS, Id: GM 47866

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