Importine

Importins are protein complexes in eukaryotes that facilitate the transport of proteins from the cytoplasm of a cell to its nucleus . Importins recognize and bind the NLS sequence on proteins and the resulting complex in turn binds to the nuclear pore complex (NPC), which is channeled into the cell nucleus using energy.

Importin complexes consist of an α and a β subunit, of which there are at least seven and four, respectively, partially cell-type-specific isoforms . Some of these subunits are able to function autonomously and have the name importin themselves. The α subunit recognizes the NLS sequence and binds it. The dimeric complex now docks to the nuclear pore with the help of the β subunit . The core protein is now transported into the core. The complex dissociates in the cell nucleus. The β-subunit bound to the Ran protein is channeled back out of the nucleus, the α-subunit is exported from the cell nucleus alone.

Web links

• Molecule of the month: Import in complex
• Jennifer McDowall / InterPro: Importins.