Importin subunit beta-1 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that in humans is encoded by the ''KPNB1''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

Function

Nucleocytoplasmic transport, a signal- and energy-dependent process, takes place through

nuclear pore complex A nuclear pore is a part of a large complex of proteins, known as a nuclear pore complex that spans the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are approximately 1,000 nuclear pore complexe ...

es embedded in the nuclear envelope. The import of proteins containing a classical

nuclear localization signal A nuclear localization signal ''or'' sequence (NLS) is an amino acid sequence that 'tags' a protein for import into the cell nucleus by nuclear transport. Typically, this signal consists of one or more short sequences of positively charged lysines o ...

(NLS) requires the NLS import receptor, a heterodimer of importin alpha and beta subunits. Each of these subunits are part of the

karyopherin Karyopherins are proteins involved in transporting 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 ...

family of proteins.

Importin Importin is a type of karyopherin that transports protein molecules from the cell's cytoplasm to the nucleus. It does so by binding to specific recognition sequences, called nuclear localization sequences (NLS). Importin has two subunits, impo ...

alpha binds the NLS-containing cargo in the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

and importin beta docks the complex at the cytoplasmic side of the nuclear pore complex. In the presence of nucleoside triphosphates and the small GTP binding protein Ran, the complex moves into the nuclear pore complex and the importin subunits dissociate. Importin alpha enters the

nucleoplasm The nucleoplasm, also known as karyoplasm, is the type of protoplasm that makes up the cell nucleus, the most prominent organelle of the eukaryotic cell. It is enclosed by the nuclear envelope, also known as the nuclear membrane. The nucleoplasm ...

with its passenger protein and importin beta remains at the pore. Interactions between importin beta and the

FG repeat Nucleoporins are a family of proteins which are the constituent building blocks of the nuclear pore complex (NPC). The nuclear pore complex is a massive structure embedded in the nuclear envelope at sites where the inner and outer nuclear membra ...

s of

nucleoporin Nucleoporins are a family of proteins which are the constituent building blocks of the nuclear pore complex (NPC). The nuclear pore complex is a massive structure embedded in the nuclear envelope at sites where the inner and outer nuclear membra ...

s are essential in translocation through the pore complex. The protein encoded by this gene is a member of the importin beta family.

Interactions

KPNB1 has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with: *

KPNA3 Importin subunit alpha-4 also known as karyopherin subunit alpha-3 is a protein that in humans is encoded by the ''KPNA3'' gene. The transport of molecules between the nucleus and the cytoplasm in eukaryotic cells is mediated by the nuclear pore ...

, * Karyopherin alpha 1, * Karyopherin alpha 2, *

Mothers against decapentaplegic homolog 3 Mothers against decapentaplegic homolog 3 also known as SMAD family member 3 or SMAD3 is a protein that in humans is encoded by the SMAD3 gene. SMAD3 is a member of the SMAD family of proteins. It acts as a mediator of the signals initiated by t ...

, * NUP153 * NUP50, *

NUP98 Nuclear pore complex protein Nup98-Nup96 is a protein that in humans is encoded by the ''NUP98'' gene. Function Signal-mediated nuclear import and export proceed through the nuclear pore complex (NPC), which is composed of approximately 30 uniq ...

, *

Nucleoporin 62 Nuclear pore glycoprotein p62 is a protein complex associated with the nuclear envelope. The p62 protein remains associated with the nuclear pore complex-lamina fraction. p62 is synthesized as a soluble cytoplasmic precursor of 61 kDa followed by ...

, *

P53 p53, also known as Tumor protein P53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory protein that is often mutated in human cancers. The p53 proteins (originally thought to be, and often s ...

, *

Parathyroid hormone-related protein Parathyroid hormone-related protein (PTHrP) is a proteinaceous hormone and a member of the parathyroid hormone family secreted by mesenchymal stem cells. It is occasionally secreted by cancer cells (for example, breast cancer, certain types of ...

, *

RANBP1 Ran-specific binding protein 1 is an enzyme that in humans is encoded by the ''RANBP1'' gene. Ran/TC4-binding protein, RanBP1, interacts specifically with GTP-charged RAN. RANBP1 encodes a 23-kD protein that binds to RAN complexed with GTP but n ...

, *

RANBP2 RAN binding protein 2 (RANBP2) is protein which in humans is encoded by the ''RANBP2'' gene. It is also known as nucleoporin 358 (Nup358) since it is a member nucleoporin family that makes up the nuclear pore complex. RanBP2 has a mass of 358 kDa. ...

, *

Ran (biology) Ran (RAs-related Nuclear protein) also known as GTP-binding nuclear protein Ran is a protein that in humans is encoded by the RAN gene. Ran is a small 25 kDa protein that is involved in transport into and out of the cell nucleus during interphase ...

, and *

SMN1 Survival of motor neuron 1 (''SMN1''), also known as component of gems 1 or ''GEMIN1'', is a gene that encodes the SMN protein in humans. Gene ''SMN1'' is the telomeric copy of the gene encoding the SMN protein; the centromeric copy is term ...

Function

Interactions

References

Further reading