Nuclear transport receptor that mediates nuclear import of proteins, such as histones, RPS3A, TNP2 and VDR ( , ). Serves as receptor for nuclear localization signals (NLS) in cargo substrates (, ). Is thought to mediate docking of the importin/substrate complex to the nuclear pore complex (NPC) through binding to nucleoporin and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism (, ). At the nucleoplasmic side of the NPC, Ran binds to the importin, the importin/substrate complex dissociates and importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran . The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus . Mediates the nuclear import of the histone H3-H4 dimer when in complex with ASF1 (ASF1A or ASF1B) (, ). Mediates the ligand-independent nuclear import of vitamin D receptor (VDR) . In vitro, mediates the nuclear import of human cytomegalovirus UL84 by recognizing a non-classical NLS .
Subcellular locations: Cytoplasm, Nucleus