IPO13
Description
The IPO13 (importin 13) is a protein-coding gene located on chromosome 1.
Importin-13 is a protein encoded by the IPO13 gene in humans. It belongs to the importin-β family of nuclear transport receptors (NTRs), responsible for shuttling molecules between the nucleus and cytoplasm. Discovered in 2000, importin-13 possesses a flexible superhelical structure with 38 α-helices, allowing it to bind a variety of cargo molecules. Its cargo binding and release mechanism differs from other importin-like receptors. Importin-13 is expressed in various human tissues including the heart, cornea, fetal lung, brain, endometrial carcinoma, and testes. Importin-13 is a unique NTR with bidirectional transport capacity, mediating both nuclear import and export of specific cargo molecules. This dual function distinguishes it from other NTRs, such as exportin 5 and exportin 4, which also exhibit bidirectional transport properties.
Importin-13 (IPO13) acts as a nuclear transport receptor, facilitating the movement of proteins into and out of the nucleus. It recognizes nuclear localization signals (NLS) in cargo proteins, enabling their import. IPO13 interacts with nucleoporins to dock the importin/cargo complex at the nuclear pore complex (NPC). Subsequently, the complex is transported through the NPC in an energy-dependent process regulated by the RanGTP gradient. Within the nucleus, RanGTP binds to importin, causing the release of the cargo. IPO13 is then re-exported to the cytoplasm, where GTP hydrolysis releases Ran. IPO13 mediates the nuclear import of various proteins, including UBC9, the RBM8A/MAGOH complex, and members of the paired homeobox family (such as PAX6). It also mediates the nuclear export of eIF-1A, with the loading of import substrates onto IPO13 triggering the release of eIF-1A in the cytoplasm.
IPO13 is also known as IMP13, KAP13, LGL2, RANBP13.
