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Co-activation of RanGTPase and inhibition of GTP dissociation by Ran-GTP binding protein RanBP1.

RCC1 (the regulator of chromosome condensation) stimulates guanine nucleotide dissociation on the Ras-related nuclear protein Ran. Both polypeptides are components of a regulatory pathway that has been implicated in regulating DNA replication, onset of and exit from mitosis, mRNA processing and transport, and import of proteins into the nucleus. In a search for further members of the RCC1-Ran signal pathway, we have identified proteins of 23, 45 and 300 kDa which tightly bind to Ran-GTP but not Ran-GDP. The purified soluble 23 kDa Ran binding protein RanBP1 does not activate RanGTPase, but increases GTP hydrolysis induced by the RanGTPase-activating protein RanGAP1 by an order of magnitude. In the absence of RanGAP, it strongly inhibits RCC1-induced exchange of Ran-bound GTP. In addition, it forms a stable complex with nucleotide-free RCC1-Ran. With these properties, it differs markedly from guanine diphosphate dissociation inhibitors which preferentially prevent the exchange of protein-bound GDP and in some cases were shown to inhibit GAP-induced GTP hydrolysis. RanBP1 is the first member of a new class of proteins regulating the binding and hydrolysis of GTP by Ras-related proteins.

Pubmed ID: 7882974


  • Bischoff FR
  • Krebber H
  • Smirnova E
  • Dong W
  • Ponstingl H


The EMBO journal

Publication Data

February 15, 1995

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Base Sequence
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Edetic Acid
  • Enzyme Activation
  • GTP Phosphohydrolases
  • Guanine Nucleotide Exchange Factors
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Nuclear Proteins
  • RNA-Binding Proteins
  • Sequence Homology, Amino Acid
  • ran GTP-Binding Protein