2bku
KAP95P:RANGTP COMPLEX
OverviewOverview
Nuclear protein import is mediated mainly by the transport factor importin-beta that binds cytoplasmic cargo, most often via the importin-alpha 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-beta consists of 19 HEAT repeats that are based on a pair of antiparallel alpha-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-beta (Kap95p or karyopherin-beta) 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-alpha or cargo. We suggest an allosteric mechanism for nuclear import complex disassembly by RanGTP.
About this StructureAbout this Structure
2BKU is a Protein complex structure of sequences from Canis lupus familiaris and Saccharomyces cerevisiae. The following page contains interesting information on the relation of 2BKU with [Importins]. Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for nuclear import complex dissociation by RanGTP., Lee SJ, Matsuura Y, Liu SM, Stewart M, Nature. 2005 Jun 2;435(7042):693-6. Epub 2005 May 1. PMID:15864302 Page seeded by OCA on Sat May 3 20:25:37 2008