Nuclear transport is an energy-dependent process mediated through saturable receptors. Export and Import receptors are by to distinguish and bind to nuclear localization signals or nuclear export signals correspondingly in the transported molecules. Receptor-substrate communication can be direct or mediated by a further adapter protein. Transport receptors dock their cargoes to the nuclear pore complexes that are also called as NPC and facilitate their translocation by the NPC. After delivering their cargoes, the receptors are recycled to initiate further rounds of transport. As a transport event for a cargo molecule is unidirectional the transport receptors engage in asymmetric cycles of translocation across the NPC.