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Updated: Jul 11, 2026

Single-Molecule Imaging of Nuclear Transport
Published on: June 9, 2010
Structural basis for the interaction between FxFG nucleoporin repeats and importin-beta in nuclear trafficking
R Bayliss1, T Littlewood, M Stewart
1MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
Abstract:
We describe the crystal structure of a complex between importin-beta residues 1-442 (Ib442) and five FxFG nucleoporin repeats from Nsp1p. Nucleoporin FxFG cores bind on the convex face of Ib442 to a primary site between the A helices of HEAT repeats 5 and 6, and to a secondary site between HEAT repeats 6 and 7. Mutations at importin-beta Ile178 in the primary FxFG binding site reduce both binding and nuclear protein import, providing direct evidence for the functional significance of the importin-beta-FxFG interaction. The FxFG binding sites on importin-beta do not overlap with the RanGTP binding site. Instead, RanGTP may release importin-beta from FxFG nucleoporins by generating a conformational change that alters the structure of the FxFG binding site.
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