The nuclear transport factor karyopherin beta binds stoichiometrically to Ran-GTP and inhibits the Ran GTPase activating protein.
The heterodimeric karyopherin functions in targeting a nuclear localization sequence (NLS)-containing protein to the nuclear pore complex followed by Ran-GTP and p10-mediated translocation of the NLS protein into the nucleoplasm. It was shown recently that Ran-GTP dissociated the karyopherin heterodimer and, in doing so, associated with karyopherin beta (Rexach, M., and Blobel, G. (1995) Cell 83, 683-692). We show here, using all recombinant yeast proteins expressed in Escherichia coli, that karyopherin beta binds to Ran-GTP and inhibits GTP hydrolysis stimulated by RanGAP (the Ran-specific GTPase activating protein). Inhibition of RanGAP-stimulated GTP hydrolysis by karyopherin beta was dependent on karyopherin beta concentration relative to Ran-GTP. Complete inhibition of RanGAP was observed at karyopherin beta concentrations that were equimolar to Ran-GTP. In gel filtration experiments, we found Ran-GTP and karyopherin beta to form a stoichiometric complex. Ran-GDP bound only weakly to karyopherin beta. We propose that stoichiometric complex formation between karyopherin beta and Ran-GTP renders Ran-GTP inaccessible to RanGAP.[1]References
- The nuclear transport factor karyopherin beta binds stoichiometrically to Ran-GTP and inhibits the Ran GTPase activating protein. Floer, M., Blobel, G. J. Biol. Chem. (1996) [Pubmed]
Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
