J Mol Biol 1998 Dec 18;2845:1517-27. doi: 10.1006/jmbi.1998.2204.

The structure of the Q69L mutant of GDP-Ran shows a major conformational change in the switch II loop that accounts for its failure to bind nuclear transport factor 2 (NTF2).

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We report the 2.3 A resolution X-ray crystal structure of the GDP-bound form of the RanQ69L mutant that is used extensively in studies of nucleocytoplasmic transport and cell-cycle progression. When the structure of GDP-RanQ69L from monoclinic crystals with P21 symmetry was compared with the structure of wild-type Ran obtained from monoclinic crystals, the Q69L mutant showed a large conformational change in residues 68-74, which are in the switch II region of the molecule which changes conformation in response to nucleotide state and which forms the major interaction interface with nuclear transport factor 2 (NTF2, sometimes called p10). This conformational change alters the positions of key residues such as Lys71, Phe72 and Arg76 that are crucial for the interaction of GDP-Ran with NTF2 and indeed, solution binding studies were unable to detect any interaction between NTF2 and GDP-RanQ69L under conditions where GDP-Ran bound effectively. This interaction between NTF2 and GDP-Ran is required for efficient nuclear protein import and may function between the docking and translocation steps of the pathway.

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Species referenced: Xenopus
Genes referenced: cdkn1a nsg1 nutf2 ran