The nuclear pore complex is the sole mediator of bidirectional transport between the nucleus and cytoplasm. Nup358 is a metazoan-specific nucleoporin that localizes to the cytoplasmic filaments and provides several binding sites for the mobile nucleocytoplasmic transport machinery. Here we present the crystal structure of the C-terminal domain (CTD) of Nup358 at 1.75Å resolution. The structure reveals that the CTD adopts a cyclophilin-like fold with a non-canonical active-site configuration. We determined biochemically that the CTD possesses weak peptidyl-prolyl isomerase activity and show that the active-site cavity mediates a weak association with the human immunodeficiency virus-1 capsid protein, supporting its role in viral infection. Overall, the surface is evolutionarily conserved, suggesting that the CTD serves as a protein-protein interaction platform. However, we demonstrate that the CTD is dispensable for nuclear envelope localization of Nup358, suggesting that the CTD does not interact with other nucleoporins.
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