関: exportin、importin、transportin

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/18 22:29:27」(JST)

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Karyopherins are a group of proteins involved in transporting molecules from the cytoplasm into the nucleus of eukaryotic cells or vice versa. The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through the nuclear pore, which acts as a gateway into and out of the nucleus. Most proteins cannot traverse through the nuclear pore by themselves, but require karyopherins.

Karyopherins, can act as importins (i.e. help proteins get into the nucleus) or exportins (i.e. help proteins get out of the nucleus). They belong to 9.A.14 The Nuclear Pore Complex Family in the transporter classification database (TCDB).

Energy for transport is derived from the ran gradient. See Ran for further details.

Importin beta example

Importin beta, a karyopherin, facilitates transport of cargo proteins into the nucleus. It does this by first binding importin alpha (another karyopherin) which binds the cargo protein in the cytoplasm. The cargo protein is imported into the nucleus through the nuclear pore, using energy derived from the Ran gradient. Once inside the nucleus, the cargo dissociates from the karyopherins. It has therefore been transported from the cytoplasm to the nucleus.

Importin beta can also carry proteins into the nucleus without the aid of the importin alpha adapter protein.^[1]

Human genes in the karyopherin family

KPNA1
KPNA2
KPNA3
KPNA4
KPNA5
KPNA6
KPNB1
CRM1

Additional images

The Ran-GTP cycle

References

^ Poon, I. K. H. and D. A. Jans (2005). "Regulation of nuclear transport: Central role in development and transformation?" Traffic 6(3): 173-186.

External links

Karyopherins at the US National Library of Medicine Medical Subject Headings (MeSH)
Illustrations at berkeley.edu
Karyopherin animations
Karyopherin illustrations

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English Journal

Differential Processing of Nuclear Pore Complex Proteins by Rhinovirus 2A Proteases from Different Species and Serotypes.

Watters K, Palmenberg AC.SourceInstitute for Molecular Virology, Robert M. Bock Laboratories, University of Wisconsin-Madison, 1525 Linden Dr., Madison, WI 53706. kewatters@wisc.edu.
Journal of virology.J Virol.2011 Oct;85(20):10874-83. Epub 2011 Aug 10.
Human rhinoviruses (HRVs) from the HRV-A, HRV-B, and HRV-C species use encoded proteases, 2A(pro) and 3C(pro), to process their polyproteins and shut off host cell activities detrimental to virus replication. Reactions attributed to 2A(pro) include cleavage of eIF4G-I and -II to inhibit cellular mRN
PMID 21835805

Nuclear transport receptor karyopherin-α2 promotes malignant breast cancer phenotypes in vitro.

Noetzel E, Rose M, Bornemann J, Gajewski M, Knuchel R, Dahl E.SourceMolecular Oncology Group, Institute of Pathology, Medical Faculty of the RWTH Aachen University, Aachen, Germany.
Oncogene.Oncogene.2011 Sep 12. doi: 10.1038/onc.2011.403. [Epub ahead of print]
Tumorigenesis and tumor progression are associated with dysfunction of the nuclear transport machinery at the level of import and export receptors (karyopherins). Recent studies have shown that the nuclear import factor karyopherin-α2 (KPNA2) is a novel prognostic marker for poor prognosis in human
PMID 21909132