Cellular component Nuclear pore complex
The nuclear pore complex (NPC) constitutes the exclusive means of nucleocytoplasmic transport in eukaryotes during interphase. NPCs allow the passive diffusion of ions and small molecules (up to about 20 kDa or 5 nm) and the active, nuclear transport receptor (karyopherin: importin and exportin)-mediated bidirectional transport of macromolecules such as proteins, RNAs, ribonucleoprotein (RNPs), and ribosomal subunits (up to about 10 MDa) across the double-membrane nuclear envelope. NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. The NPC is composed of at least 30 distinct subunits, shows 8-fold rotational symmetry with specialized structures on the cyto- and nucleoplasmic side and in the nuclear envelope embedded core. The MW varies from about 44-60 MDa in S. cerevisiae to 60-120 MDa in vertebrates, yet the overall architecture is conserved.
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