Structure of the nuclear transport complex karyopherin-beta2-Ran x GppNHp

Nature. 1999 May 20;399(6733):230-7. doi: 10.1038/20375.

Abstract

Transport factors in the karyopherin-beta (also called importin-beta) family mediate the movement of macromolecules in nuclear-cytoplasmic transport pathways. Karyopherin-beta2 (transportin) binds a cognate import substrate and targets it to the nuclear pore complex. In the nucleus, Ran x GTP binds karyopherin-beta2 and dissociates the substrate. Here we present the 3.0 A structure of the karyopherin-beta2-Ran x GppNHp complex where GppNHp is a non-hydrolysable GTP analogue. Karyopherin-beta2 contains eighteen HEAT repeats arranged into two continuous orthogonal arches. Ran is clamped in the amino-terminal arch and substrate-binding activity is mapped to the carboxy-terminal arch. A large loop in HEAT repeat 7 spans both arches. Interactions of the loop with Ran and the C-terminal arch implicate it in GTPase-mediated dissociation of the import-substrate. Ran x GppNHp in the complex shows extensive structural rearrangement, compared to Ran GDP, in regions contacting karyopherin-beta2. This provides a structural basis for the specificity of the karyopherin-beta family for the GTP-bound state of Ran, as well as a rationale for interactions of the karyopherin-Ran complex with the regulatory proteins ranGAP, ranGEF and ranBP1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Biological Transport
  • Cell Nucleus / metabolism
  • Crystallography, X-Ray
  • Escherichia coli
  • Guanosine Triphosphate / chemistry
  • Guanosine Triphosphate / metabolism
  • Guanylyl Imidodiphosphate / chemistry*
  • Guanylyl Imidodiphosphate / metabolism
  • Humans
  • Karyopherins
  • Macromolecular Substances
  • Models, Molecular
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / metabolism
  • Protein Conformation
  • Receptors, Cytoplasmic and Nuclear / chemistry*
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Repetitive Sequences, Amino Acid
  • ran GTP-Binding Protein

Substances

  • Karyopherins
  • Macromolecular Substances
  • Nuclear Proteins
  • Receptors, Cytoplasmic and Nuclear
  • Recombinant Proteins
  • Guanylyl Imidodiphosphate
  • Guanosine Triphosphate
  • ran GTP-Binding Protein

Associated data

  • PDB/1QBK