Karyopherin
Encyclopedia
Karyopherins are a group of protein
s involved in transporting
molecules from the cytoplasm
into the nucleus
of eukaryotic cell
s. 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 importin
s (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.
, 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.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s involved in transporting
Transport protein
A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. Transport proteins are integral membrane proteins; that is they exist within and span the membrane across which they...
molecules from the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
into the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of eukaryotic cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s. The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through the nuclear pore
Nuclear pore
Nuclear pores are large protein complexes that cross the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are about on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate cell, but it varies depending on cell type and the stage in...
, 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 importin
Importin
Importin is a type of protein that moves other protein molecules into the nucleus by binding to a specific recognition sequence, called the nuclear localization signal . Importin is classified as a karyopherin....
s (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 poreNuclear pore
Nuclear pores are large protein complexes that cross the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are about on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate cell, but it varies depending on cell type and the stage in...
, 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.
Human genes in the karyopherin family
- KPNA1KPNA1Importin subunit alpha-1 is a protein that in humans is encoded by the KPNA1 gene.-Interactions:Karyopherin alpha 1 has been shown to interact with KPNB1 and UBR5.-Further reading:...
- KPNA2KPNA2Importin subunit alpha-2 is a protein that in humans is encoded by the KPNA2 gene.The import of proteins into the nucleus is a process that involves at least 2 steps. The first is an energy-independent docking of the protein to the nuclear envelope and the second is an energy-dependent...
- KPNA3KPNA3Importin subunit alpha-3 is a protein that in humans is encoded by the KPNA3 gene.-Further reading:...
- KPNA4KPNA4Importin subunit alpha-4 is a protein that in humans is encoded by the KPNA4 gene.-Further reading:...
- KPNA5KPNA5Importin subunit alpha-6 is a protein that in humans is encoded by the KPNA5 gene.-Further reading:...
- KPNA6KPNA6Importin subunit alpha-7 is a protein that in humans is encoded by the KPNA6 gene.-Further reading:...
- KPNB1KPNB1Importin subunit beta-1 is a protein that in humans is encoded by the KPNB1 gene.-Interactions:KPNB1 has been shown to interact with NUP98, Karyopherin alpha 1, KPNA3, Karyopherin alpha 2, SMN1, Parathyroid hormone-related protein, Nucleoporin 62, RANBP2, Ran , RANBP1, NUP50, P53, NUP153 and...
- CRM1