Karyopherins and nuclear import

Proteins of the karyopherin α and karyopherin β families play a central role in nucleocytoplasmic transport. Recently, crystal structures of karyopherin α and its complexes with nuclear localization signal peptides, a karyopherin β2–Ran complex and complexes of full-length and fragments of karyopherin β1 with import substrates, Ran and nucleoporins have been solved. These karyopherin structures provide valuable insights into understanding the molecular mechanism of nuclear import, especially substrate recognition, substrate release by GTPase and interactions with the nuclear pore complex.