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Nucleoporin
The 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 that extends across the nuclear envelope, forming a gateway that regulates the flow of macromolecules between the cell nucleus and the cytoplasm. Nuclear pores in turn allow the transport of water-soluble molecules across the nuclear envelope. Nucleoporins, a family of around 30 proteins, are the main components of the nuclear pore complex in eukaryotic cells. Nucleoporin 62 is the most abundant member of this family.〔Han I, Oh ES, Kudlow JE (2000). "Responsiveness of the state of O-linked N-acetylglucosamine modification of nuclear pore protein p62 to the extracellular glucose concentration". Biochem. J. 350 Pt 1 (Pt 1): 109–14. doi:10.1042/0264-6021:3500109. PMC 1221231. PMID 10926833.〕 Nucleoporins are able to transport molecules across the nuclear envelope at a very high rate. A single NPC is able to transport 60,000 protein molecules across the nuclear envelope every minute.〔
==Function==
Nucleoporins mediate transport of macromolecules between the cell nucleus and cytoplasm in eukaryotes. Certain members of the nucleoporin family form the structural scaffolding of the nuclear pore complex. However, nucleoporins primarily function by interacting with transport molecules known as karyopherins, also known as Kaps These karyopherins interact with nucleoporins that contain FG peptide repeats, that is, they contain repeating sequences of the amino acids phenylalanine (F) and glycine (G). In doing so, karyopherins are able to shuttle their cargo across the nuclear envelope. Nucleoporins are only required for the transport of large hydrophilic molecules above 40 kDa, as smaller molecules pass through nuclear pores via passive diffusion. Nucleoporins play an important role in the transport of mRNA from the nucleus to the cytoplasm after transcription. Depending on their function, certain nucleoporins are localized to a single side of the nuclear pore complex, either cytosolic or nucleoplasmic. Other nucleoporins may be found on both faces. Interestingly, it has been recently shown that FG nucleoporins have specific evolutionary conserved features encoded in their sequences that provide insight into how they regulate the transport of molecules through the nuclear pore complex (NPC).
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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