Nucleo-cytoplasmic transport comprises a large number of distinct pathways, many of which are defined by members of the importin beta superfamily of nuclear transport receptors. These transport receptors all directly interact with RanGTP to modulate the compartment-specific binding of their transport substrates. RanBP17 is a novel RanGTP-binding protein that interacts with the nuclear pore complex and is able to enter the nucleus independent of energy and additional nuclear transport receptors.