Protein sorting lec 1 (lec8)

Question 1

When targeting to the ER?

Answer 1

Hydrophobic signal sequence (often at N-terminus) is used

Question 2

What is contained within the hydrophobic signal sequence?

Answer 2

Cleavage site

Question 3

how large is the hydrophobic signal sequence?

Answer 3

18-15 amino acids long

Question 4

Function of proteases on the hydrophobic signal sequence?

Answer 4

Create a new n terminus

signal peptidase

Question 5

When a signal emerges from the ribosome it is recognised by?

Answer 5

Ribonucleoprotein- a complex made up of RNA and proteins

Question 6

SRP

Answer 6

Signal recognition particle

Question 7

Binding of the SRP to signal sequence and ribosome?

Answer 7

Halts translation

Question 8

If a protein does not have a SRP then??

Answer 8

Translation will continue

Question 9

SRP-receptor is located? Function?

Answer 9

Within the membrane of the ER

function: binds to the Ribosome/nascent chain/SPR complex

Question 10

Nascent chain??

Answer 10

Is the partially synthesised protein

Question 11

SRP does what job?

Answer 11

Guides the complex (Ribosome/nascent chain/SPR complex) to the translocon

Question 12

Translocon ?

Answer 12

Protein conduction channel within the ER membrane

Question 13

When the translocon engages with the SRP and SRP receptor what occurs (3)

Answer 13

GTP hydrolysis,
and therefore a conformational change in both SRP and the SRP receptor (loose affinity for each-other)
SRP unbinds from the complex and can be recycled for the same process

Question 14

Once SRP released from the ribosome what can resume??

Answer 14

Translation

Question 15

How does the chain actually move through the ER membrane

Answer 15

• Via translation

Question 16

What assists with translocation of the protein??

Answer 16

Lumenal proteins

Question 17

What conformational change occurs when the protein is transported through the er membrane?

Answer 17

Unfolded

Question 18

At what point foes the chain begin to emerge from the ribosome?

Answer 18

30 amino acids

Question 19

Lumenal protein formation?

Answer 19

Cleaved by Singal peptidase protein complex creating a New n- terminus

Question 20

Transmembrane proteins are located?

Answer 20

Not within the lumen, but throughout the membrane (within the membrane- Integral membrane protein)

Question 21

Transmembrane proteins are not?

Answer 21

Cleaved, no new n terminus

Question 22

Size of hydrophobic stretches on transmembrane proteins? Why?

Answer 22

Longer hydrophobic stretches of amino acids (greater than 15)

as they will be located within a hydrophobic environment

Question 23

Proteins targeted to ER

Answer 23

start synthesis in cytosol

Question 24

Chaperones

Answer 24

Maintained protein in an unfolded state

Question 25

Proteins are what in terms of their movement

Answer 25

Mobile

Question 26

Endomembrane system

Answer 26

All the organelles/membranes of the secretory and endocytic patheways (ER, Golgi, lysosomes, plasma membrane, endosomes

Question 27

Anterograde

Answer 27

Forward pathways

Question 28

Retrograde

Answer 28

Backwards pathways

Question 29

Endocytic pathways

Answer 29

onsists of distinct membrane compartments

Question 30

Vesicle buds from

Answer 30

donor compartment

Question 31

One the vesicle translocates to the acceptor compartment ?

Answer 31

Fusion, docks with it

Question 32

Packaging into vesicles that bud from an organelle is ________

Answer 32

selective

Question 33

Buds form with the help of?

Answer 33

Coats

Question 34

Coats do what to the membrane conformation

Answer 34

physically deform

Question 35

Example of a coat

Answer 35

Clathrin

Question 36

Coats interact with?

Answer 36

Cargo receptors on the cytoplasmic domain

Question 37

There is no direct interaction between?

Answer 37

Coats and cargo

Question 38

Triskelion structure

Answer 38

Heavy and light chain

Question 39

Example of a type of physical deformation of membrane ?

Answer 39

Spherical shape by forming cages

Question 40

Scisson event of Clathrin coat?

Answer 40

protein: Dynamin (GTPase)

Consitrcis the membrane and forces to fuse

Question 41

Experiment which prooved the action of dyamin

Answer 41

drosophila mutant dynamin
become paralysed
cannot endocytose membrane of synaptic vesicles

Question 42

budding from the Golgi and from the plasma membrane is associated with which coat?

Answer 42

Clathrin coated vesicles

Question 43

COP coat examples and are associated with trafficking proteins from?

Answer 43

COPI - GOLGI to ER

COPII- ER to Golgi