Recombinant Saccharomyces cerevisiae Importin subunit beta-3 (PSE1), partial

Functions in nuclear protein import as nuclear transport receptor. Serves as receptor for classical and arginine/glycine-rich nuclear localization signals (cNLS and rg-NLS) in cargo substrates. Its predominant cargo substrate seems to be ribosomal proteins and ribosome biogenesis trans- and cis-acting factors. Required for nuclear transport of YAP1, NOP1 and SOF1. Mediates the nuclear import of histones H3 and H4. Mediates docking of the importin/substrate complex to the nuclear pore complex (NPC) through binding to repeat-containing nucleoporins. The complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, GTP-Ran binding leads to release of the cargo. The importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. 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.; Plays a role in protein secretion.