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13 Cards in this Set

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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

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

What is the Classical NLS?

K-K-K-R-K

What is the common, non-classical NS?

PY - prolyine-tyrosine

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

Which NLS receptors recognize which NLS?

1. Importin: Classic


2. Transportin: PY


3. Snurportin: other

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

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

what does ran gtp do for import?

it binds to beta subunit so it lets go of alpha+cargo

what are NES's? what types are there?

nuclear export signals


1. Leucine-rich



What is exportin1?

1. Trimeric (3 subunits)


2. binds nes cargo and rangtp


3. recognizes leucine rich NES

What are the 3 proposed types of nuclear import?

1. waving filament model


2. FG mesh model


3. increasing affinity binding model