Biol110-10-Lecture 7-Nuclear Import

Biol110-10-Lecture 7-Nuclear Import - The nuclear envelope...

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Unformatted text preview: The nuclear envelope imposes a diffusion barrier between the cytoplasm and the nucleoplasm nucleoplasm 8-25 nm gold facilitated diffusion < 30 kDa or 3 nm The nuclear pore complex permits the passage of only small particles by passive (free) diffusion What is the gate made of? Small gold 1-4 nm Location of the diffusion gate(s) at the nuclear pore complex Cytoplasmic injection Nucleoplasmic injection Large gold 8-24 nm Gate #1 Gate #2 C. Feldherr et al Nuclear import and export of large proteins and RNP’s requires karyopherins and Ran; Ran imparts directionality + Ntf2 (p10) + Karyopherin The compartmentalization of RanGTP and RanGDP Ran’s nucleocytoplasmic trafficking Major questions in karyopherin-mediated transport across the NPC- I. How does the structure and composition of the nuclear pore complex relate to its transport function? II. What are the kinetics of transport? III. What are the mechanics of karyopherin movement across the NPC? IV. How is directionality of transport achieved? V. How is the NPC permeability barrier maintained while karyopherins transport cargos of different shapes and sizes? Creating a topographic map of the Nuclear Pore Complex using cryo-electron microscopy- Visualization of vertebrate NPC’s in Xenopus (frog) annulate lamella using cryo-EM. Purification of the yeast nuclear pore complex and identification of its subunits- The nucleoporin components of the purified yeast NPC and their sub-location FG Nups Nup1 Nup2 Nup42 Nup49 Nup53 Nup57 Nup59 Nup60 Nup100 Nup116 nNup145 Nup159 Nsp1 Non FG Nups Nup82 Nup84 Nup85 Nup120 Nup133 cNup145 Nup157 Nup170 Nup188 Nup192 Sec13 Seh1 Cdc31 Nic96 POMs Pom34 Pom152 Ndc1 Sub-localization of nucleoporins by immuno-EM The ring The gate http://www.nature.com/nature/journal/v450/n7170/extref/nature06405-s1.mov Molecular architecture of the yeast nuclear pore complex The nuclear pore complex by cryo-EM The nuclear pore complex by computer reconstruction A family of nucleoporins with multiple phenylalanine-glycine repeats nNup145p FG Nups N C FG repeat coiled-coil domain FG repeat regions of Nups are natively unfolded and resemble random coils- Evidence: •Peculiar amino acid composition •Large hydrodynamic dimensions •Lack of secondary structure •Hypersensitivity to proteases in situ Nup159p 90% random coil Nup2p 80% random coil Nup1p 90% random coil Nsp1p 95% random coil Nup100p 80% random coil FG regions are typically 200-700 AA long Two structural categories of disordered FG domains: compacted and extended The FG nucleoporins (FG Nups) are natively unfolded and function collectively at the NPC as a hypothetical filamentous meshwork ~150 FG Nups ~30% of the NPC mass What is the advantage of having natively unfolded proteins in the central conduit?...
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This note was uploaded on 01/17/2011 for the course BIOL 110 taught by Professor Rexach during the Fall '10 term at UCSC.

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Biol110-10-Lecture 7-Nuclear Import - The nuclear envelope...

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