title: Dissociation of nuclear import cargo complexes by the protein Ran: a fluorescence correlation spectroscopy study.
abstract: In nucleated cells, proteins designed for nuclear import form complexes with soluble nuclear transport receptors prior to translocation across the nuclear envelope. The directionality of transport is due to the asymmetric distribution of the protein Ran, which dissociates import cargo complexes only in its nuclear RanGTP form. Using fluorescence correlation spectroscopy, we have studied the stability of cargo complexes in solution in the presence and in the absence of RanGTP. We find that RanGTP has a higher affinity for the major import receptor, the importin alpha/beta heterodimer, when importin alpha does not carry a cargo, suggesting that some nuclear transport targets might be preferentially released.
authors.affiliation: Department of Physics and Astronomy, 1280 Main St. W, Hamilton, ON, L8S4M1, Canada. fradin@physics.mcmaster.ca
authors.forename: Cécile
authors.initials: C
authors.lastname: Fradin
authors.forename: David
authors.initials: D
authors.lastname: Zbaida
authors.forename: Michael
authors.initials: M
authors.lastname: Elbaum
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008962:Models, Theoretical; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology*; D013050:Spectrometry, Fluorescence / Q000379:methods; D020931:ran GTP-Binding Protein / Q000378:metabolism*
chemical_list: D028884:Karyopherins; D010446:Peptide Fragments; D020931:ran GTP-Binding Protein