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13 Cards in this Set
- Front
- Back
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what are FG repeats and where are they found? |
They are phenylalanine-glycine repeats found in 1/3 proteins in nuclear pores. They act as binding sites for importin, transportin, and snurportin |
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what are the 2 types of nuclear transport and what do they allow? |
1. Passive diffusion: allows transport of - small molecules like ions, nucleotides - small proteins < 40 kDA 2. Receptor mediated transport: - nuclear proteins >40 kda - newly assembled ribosomes - mRNA tRNA |
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What is the Classical NLS? |
K-K-K-R-K |
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What is the common, non-classical NS? |
PY - prolyine-tyrosine |
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What are the rules for NLS? |
- they can be anywhere in the protein - they are not cleaved off after entry because they are needed for reentry after mitosis |
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Which NLS receptors recognize which NLS? |
1. Importin: Classic 2. Transportin: PY 3. Snurportin: other |
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How does importin mediated import work? |
1. Beta + alpha recognize NLS 2. alpha binds to cargo and beta binds to alpha 3. beta binds to fg's on nuclear pore proteins |
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How does import receptor know which way to go? |
There's a RAN-GTP gradient/GDP gradient. Ran GTP is only in nucleus and GDP is primarily in cytoplasm |
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what does ran gtp do for import? |
it binds to beta subunit so it lets go of alpha+cargo |
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what are NES's? what types are there? |
nuclear export signals 1. Leucine-rich |
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What is exportin1? |
1. Trimeric (3 subunits) 2. binds nes cargo and rangtp 3. recognizes leucine rich NES |
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What are the 3 proposed types of nuclear import? |
1. waving filament model 2. FG mesh model 3. increasing affinity binding model |
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