Karyopherin

Karyopherins are a group of proteins involved in transporting molecules from the cytoplasm into the nucleus of eukaryotic cells. 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) and then the cargo protein in the cytoplasm. Import into the nucleus then occurs through the nuclear pore, with the required energy being derived from the Ran gradient. When 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.

=Human genes in the karyopherin family=
 * KPNA1
 * KPNA2
 * KPNA3
 * KPNA4
 * KPNA5
 * KPNA6
 * KPNB1
 * CRM1

=Additional images=

=References=

=External links=
 * Illustrations at berkeley.edu
 * Karyopherin animations
 * Karyopherin illustrations
 * Karyopherin illustrations

Carioferina Karyophérine