Importin subunit beta-1 (importin beta-1) functions in nuclear protein import, either in association with an adapter protein, such as an importin-alpha subunit, which binds to nuclear localization signals (NLS) in cargo substrates, or by acting as autonomous nuclear transport receptor. Acting autonomously, importin beta-1 functions as a NLS receptor. Docking of the importin/substrate comple, Xenopus/Amphibian, to the nuclear pore comple, Xenopus/Amphibian, (NPC) is mediated by importin beta-1 through binding to nucleoporin F, Xenopus/Amphibian,FG repeats and the comple, Xenopus/Amphibian, is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism.