Large molecules are constantly shuffled between the nucleus and cytoplasm via channels called nuclear-pore complexes. Transport is mediated by receptor proteins called importins and exportins, which bind the cargo and shuttle it through the pore. The crystal structures of two importins — one with its cargo and one with the GTP-bound form of the small GTPase Ran — are now reported. There are telling similarities and differences between these two structures.
- Iain W. Mattaj
- Elena Conti
