Use this URL to cite or link to this record in EThOS:
Title: The role of FxFG-repeat nucleoporins in nuclear trafficking
Author: Bayliss, R. W. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
Availability of Full Text:
Full text unavailable from EThOS.
Please contact the current institution’s library for further details.
Trafficking of macromolecules between the nucleus and cytoplasm through nuclear pore complexes (NPCs) is an essential process in eukaryotic cells. For example, proteins containing a nuclear localisation sequence (NLS) are imported into the nucleus, whereas proteins containing a nuclear export sequence (NES) are exported into the cytoplasm. Many nucleoporins, the proteins from which NPCs are constructed, contain FxFG-repeats, sequences based on a hydrophobic core (of sequence PhexPheGly, where x is usually a small residue) and a hydrophilic linker. Previous work has shown that carrier molecules, including importin-β and Nuclear Transport Factor 2 (NTF2), bind to FxFG-repeats, and addition of soluble FxFG-repeats inhibits nuclear trafficking processes. This Thesis characterises the interactions between FxFG nucleoporin repeats and both NTF2 and importin-β. Binding studies on a rationally-designed NTF2 mutant localise the FxFG binding site to near Trp7. Although I show that the interaction between FxFG repeats and NTF2 is weak, I also show that the interaction is essential for NTF2 to mediate the nuclear import of Ran in permeabilised cells. An X-ray crystal structure of importin-β (residues 1-442) in complex with FxFG repeats is presented which shows, for the first time, how FxFG-repeats interact with a carrier molecule. The crystal structure is used to produce mutants of full-length importin-β which are deficient in FxFG repeat binding, and yet retain binding to RanGTP and importin-α. These mutants are used to demonstrate that an interaction with FxFG repeats is essential for importin-β to mediate nuclear protein import of a substrate containing a classical NLS. A model for how RanGTP may release importin-β from FxFG repeats is proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available