Block 1: Nucleocytoplasmic Transport

Question 1

______ is continuous with the ER and therefore is studded with ribosomes

Answer 1

Outer nuclear membrane

Question 2

Nuclear lamina is associated with the _____ and is composed of ______. Dimers of ____ and ____ form

Answer 2

Nuclear lamina

Intermediate Filaments

Lamin A and Lamin B form a meshwork of protein that binds chromatin

Question 3

Molecules less than ____ can enter/exit by diffusion through pores. Rate of diffusion is about______. These particles move____.

Answer 3

less than 60kDa

about 1/(molecular mass^1/2)

Particles move down conc. gradient

Question 4

Particles greater than ____ are transported using ____.

First NLS discovered was ______. Most NLS have _____.

Answer 4

greater than 60 kDa

active transport using a leucine rich nuclear export sequence (NES) or Nuclear Localization Signal (NLS).

PKKKRKV. Most have strings of basic AAs.

• can artificially add NLS

Question 5



Question 6

Question 7

1. On cytoplasmic side, ____ is high and ____ is low.
2. ______ protein is present to _______.
3. ______ pick up cargo and _____ drop it off.

Answer 7

Ran-GDP is high, Ran-GTP is low.

Ran-GAP (GTPase activating protein) is present to hydrolyze GTP–> GDP

Importins pick up cargo and exportins drop it off.

Question 8

1. On nuclear side, _____ is high and ____ is low.
2. ______ protein is present to _______.
3. ______ drop off cargo and _____ pick it up.

Answer 8

Ran-GTP is high and Ran-GDP is low.

Ran-GEF (Guanine Nucleotide Exchange Factor) is present to add a fresh GTP to Ran

Importins drop off cargo and exportins pick it up.