Karyopherin

Karyopherins are transport proteins involved in the nuclear transport of moving molecules between the cytoplasm and the nucleus of a eukaryotic cell. (The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through nuclear pores which act as gateways into and out of the nucleus. Macromolecular proteins require karyopherins to traverse the nuclear pore.

Karyopherins can act as importins helping proteins to enter the nucleus, or as exportins helping proteins to exit the nucleus. They belong to the nuclear pore complex family in the transporter classification database (TCDB). Energy for transport is derived from the Ran gradient.

Upon stress, several karyopherins stop shuttling between the nucleus and the cytoplasm and are sequestered in stress granules, cytoplasmic aggregates of ribonucleoprotein complexes.

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