Nuclear pore complex Clause Samples

Nuclear pore complex. The NPC is a massive protein complex that forms the gateway through the nuclear envelope, connecting the nucleus with the cytoplasm. Composed of multiple copies of ~30 nucleoporins (Nups) in eightfold symmetry, the NPC is a staggering ~120 MDa complex extending approximately 125 nm from the cytoplasmic fibrils to the nuclear basket (▇▇▇▇ and ▇▇▇▇▇ 2006). The central channel can expand so that it is large enough to accommodate transport of ribosome subunits (Kohler and Hurt 2007). The NPC regulates movement into and out of the nucleus. Ions and molecules smaller than 40 kDa freely diffuse through the nuclear pore while molecules larger than 40 kDa require the assistance of nuclear transport receptors to travel through the NPC. A single NPC can accommodate more than 1,000 transport events per second (▇▇▇▇▇▇▇ and Gorlich 2001) and a nucleus has thousands of NPCs to fill the constant need for cargo delivery. While the exact structure of the NPC and precise mechanism of selective transport have not been determined, some of the roles of NPC components in these processes have been established. Nup84 plays a role in regulating positioning and spacing of NPCs in the nuclear envelope (▇▇▇▇, King et al. 2014), and the transmembrane proteins POM121, NDC1, and Nup210 anchor the NPC in the nuclear envelope (▇▇▇▇▇, Shows et al. 2007). Structural Nups of the Nup107-160 complex (Nups160, 107, 133, 96, 85, 43, 37, ▇▇▇▇▇, ▇▇▇▇, and ELYS) provide the NPC’s general architecture (Walther, ▇▇▇▇▇ et al. 2003, ▇▇▇▇▇, Shows et al. 2007). These core structural Nups are very stably associated in the NPC, and the same protein can persist in the complex for years in post-mitotic cells (Savas, Toyama et al. 2012, ▇▇▇▇▇▇, ▇▇▇▇▇ et al. 2013). Other Nups associate with the NPC more dynamically, with dwell times ranging from hours to seconds (▇▇▇▇▇, ▇▇▇▇ et al. 2004). Among these more dynamic Nups are the proteins that make up the cytoplasmic face of the nuclear pore, the hydrophobic Nups of the central channel, and the proteins that make up the nuclear basket. A cargo’s passage through the NPC begins and ends with interaction with cytoplasmic filaments and the nuclear basket. Cytoplasmic filaments are made up of Nup358 and Nup214. Long filamentous domains of these proteins extend into the cytoplasm and provide binding sites for transport proteins. Nuclear import begins with binding of NTR-cargo complexes to cytoplasmic filaments. Nuclear export terminates with RanGAP-mediated dissociation ...