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- Title
Structural basis for nuclear import complex dissociation by RanGTP.
- Authors
Lee, Soo Jae; Matsuura, Yoshiyuki; Liu, Sai Man; Stewart, Murray
- Abstract
Nuclear protein import is mediated mainly by the transport factor importin-β that binds cytoplasmic cargo, most often via the importin-α adaptor, and then transports it through nuclear pore complexes. This active transport is driven by disassembly of the import complex by nuclear RanGTP. The switch I and II loops of Ran change conformation with nucleotide state, and regulate its interactions with nuclear trafficking components. Importin-β consists of 19 HEAT repeats that are based on a pair of antiparallelα-helices (referred to as the A- and B-helices). The HEAT repeats stack to yield two C-shaped arches, linked together to form a helicoidal molecule that has considerable conformational flexibility. Here we present the structure of full-length yeast importin-β (Kap95p or karyopherin-β) complexed with RanGTP, which provides a basis for understanding the crucial cargo-release step of nuclear import. We identify a key interaction site where the RanGTP switch I loop binds to the carboxy-terminal arch of Kap95p. This interaction produces a change in helicoidal pitch that locks Kap95p in a conformation that cannot bind importin-α or cargo. We suggest an allosteric mechanism for nuclear import complex disassembly by RanGTP.
- Subjects
ALLOSTERIC regulation; PHYSIOLOGICAL control systems; EDIBLE fungi; NUCLEAR matrix; CYTOPLASM; NUCLEOTIDE sequence
- Publication
Nature, 2005, Vol 435, Issue 7042, p693
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature03578