Protein Sorting I

Question 1

How does transport between nucleus and cytosol work?

Answer 1

Gated Transport.
Through nuclear pore complexes
It also allows for active transport and free diffusion

Question 2

What type of transport happens between the cytosol and organelle membranes?

Answer 2

Transmembrane Transport

Uses protein translocators that directly transport specific proteins.

Question 3

What type of membrane-enclosed transport intermediates move proteins between the various compartments via vesicles?

Answer 3

Vesicular transport

Question 4

What removes a signal sequence once the protein arrives at the destination?

Answer 4

signal peptidases

Question 5

Signal sequences are both:

Answer 5

necessary and sufficient for protein targeting

Question 6

Physical properties of the sequence is more important than

Answer 6

the actual sequence.

Question 7

What recognizes the signal?

Answer 7

complementary receptors

Question 8

What is the zipcode for the nucleus?

Answer 8

Lys-Lys-Lys-Arg-Lys

Question 9

What is the zipcode to leave the nucleus

Answer 9

Met-x-x-Leu-x-x-x-Leu-x-x-x-Phe

Question 10

What is the zipcode to get into the mitochondria?

Answer 10

N-Term-x-x-x-x-ARG-x-x-x-x-Arg-x-x-x-Arg-x-x Lys-x-x-x-Arg-x-x-xArg-x-x-x

scattered integrated positive charge

Question 11

Zipcode for getting in to the ER:

Answer 11

N-term-x-x-x-x-x-x-xLeu-leu-leu-val-gly-ile=leu=phe=prp=ala-x-x-x-x

All positively charged aa, and one negatively charged

Question 12

Zipcode to return to the ER

Answer 12

-Lys-Asp-Glu-Leu

Question 13

What are the proteins that are needed from the cytosol in the nucleus?

Answer 13

histones, dna, rna polymerases, topoisomerase, gene regulatory proteins.

Question 14

What proteins/molecules are made in the nucleus and sent to the cytosol?

Answer 14

tRNA and mRNA

Question 15

What are the 30 different proteins of the nuclear envelope called?

Answer 15

NUCLEOPORINS

Question 16

What is the geometric shape of the nuclear pores?

Answer 16

octagonal symmetry with one or more aqueous pores.

Question 17

Going through the nuclear pore: SMALL MOLECULES… How?

Answer 17

Passive diffusion and facilitated transport

Question 18

Transport into the nuclear pore complex is facilitated by binding of particles to :

Answer 18

fibrils… extending from the NPC

Question 19

What is an NLS?

Answer 19

it’s a zipcode or sorting signal for the protein to go to the nucleus

Question 20

What is the physical property of the NLS?

Answer 20

Positively charges Lys and Arg (They need to be right next to each other, no interruptions)

Question 21

Where are the LYS and ARG on the protein for the NLS?

Answer 21

different sites on the protein, forms loops or patches on the surface

Question 22

The NLS is recognized by what?

Answer 22

NIRs: Nuclear Import Receptors

Question 23

What is an NIR?

Answer 23

soluble cytosolic proteins that bind to the NLS on protein and to the NPC proteins present on fibrils that extend into the cytoplasm.

Question 24

The Nuclear pore complex has Phenylalanine glycine repeats called:

Answer 24

FG repeats

Question 25

What do the FG repeats do?

Answer 25

act as a binding site for import receptors.

Question 26

What are the steps of going through the NPC?

Answer 26

binding
Dissociating
Re-binding

Question 27

zipcode to get out of the nucleus?

Answer 27

NES: Nuclear export signal, needs complementary export receptor (NER)
NER binds to cargo present in the nucleus and the NPC proteins

Transport out happens the same say: binding, dissociation, rebinding

Question 28

GAP or GTPase activating protein is found on which side?

Answer 28

cytosol

Question 29

GEF or Guanine exchange factor is found on which side?

Answer 29

nuclear

Question 30

what does the GEF do?

Answer 30

it bumps the GDP off RNA and exchanges it for GTP, therefore activates it.
GEF activates.

Ran-GTP gets you out of the nucleus