KPNB1 is a member of the importin beta family. The KPNB1 protein is engaged in nuclear protein import， either by coupling itself with an adapter protein （e.g.， importin-alpha subunit which binds to nuclear localization signals （NLS） in cargo substrates）， or by functioning autonomously as a nuclear transport receptor （acts as NLS receptor， docking of the importin/substrate complex to the nuclear pore complex）.
