Protein Sorting and protein trafficing LEC 1 (LEC7 TOTAL)

Question 1

Protein makeup of different organelles within a cell.

Answer 1

Varied

Question 2

On average, how many proteins within a cell?

Answer 2

10 billion

Question 3

Examples of the protein types which may be found in mitochondria?

Answer 3

Electron transport chain proteins (integral)

Question 4

Protein property- movement

Answer 4

NOT static. Can move between different areas within a cell. DYNAMIC.

Question 5

How many mitochondrial proteins on average are there and how many are actually synthesised within the mitochondria itself?

Answer 5

13/1000

Question 6

if proteins are not sorted correctly?

Answer 6

Chemical chaos

Question 7

Where does protein sorting start?

Answer 7

Cytosol- the aq compartment of the cytoplasm in which organelles are embedded.

Question 8

Exceptions in which protein does not occur in the cytosol/cytoplasm?

Answer 8

Chloroplasts and mitochondria

Question 9

Sorting signals function?

Answer 9

Provide information in which where a protein should go (analogy: post code).

specific stretches of amino acids in proteins.

Question 10

Cellular machineries function?

Answer 10

recognise sorting signals and facilitate the sorting

Question 11

Different places in which sorting signals provide information to which are a protein should be localised.

Answer 11

nucleus
mito
ER

Question 12

How does nuclear targeting enable recognition by cellular machinery?

Answer 12

Positively charged amino acid contain one or more stretches.

One stretch- continuous

multiple: discontiuous

either way: fold up into 3D structure and form a patch.

Question 13

Experimental evidence for nuclear targeting?

Answer 13

mutagenesis of a single Amino acid lysine for Thr.

Virus: T-ANTIGEN

normally targeted to the nucleus.

Now to cytoplasm only (with mutation)

Question 14

Architecture of the nuclear membrane?

Answer 14

Double membrane which is contiguous with the ER.

Question 15

Lumen characteristic of the nucleus?

Answer 15

Lumen of the nuclear membrane is continuous with the lumen of the ER.

Question 16

Molecular composition of the nuclear pores?

Answer 16

Complex protein structures

Question 17

Fibrils extend in which direction?

Answer 17

both in and out of the nuclear membrane

Question 18

Small molecule diffusion within the nuclear pores?

Answer 18

freely permeable

Question 19

Pore size (nuclear)

Answer 19

relatively large

Question 20

Larger molecules mechanism in which they move through the nuclear pores?

examples of large molecule sin which do this?

Answer 20

Proteins and mRNA

Actively transported (require energy)

Question 21

Name for proteins?

Answer 21

Cargo

Question 22

NLS

Answer 22

nuclear localisation sequences

Question 23

NLS recognised by?

Answer 23

nuclear import receptors

Question 24

Where are NIR found?

Answer 24

fibrils

Question 25

NIR?

Answer 25

nuclear import receptors

Question 26

What occurs when the nuclear protein binds to fibrils?- physical change

Answer 26

pore opens

Question 27

Characteristic of nuclear import receptors?

Answer 27

Bind to different cargoes

- specific binding to NIR

Question 28

Protein imported in what state?

Answer 28

Folded- 3D structure

Question 29

What occurs after the binding of the NLS to the NIR?

Answer 29

Transported to the nuclear pore (currently attached to fibrils)

Question 30

Once the nuclear import receptor cargo complex is released into the nucleus, what occurs?

Answer 30

Ran- GTP which has a higher affinity for nuclear import receptor. Therefore binding, and being released back into the cytosol.

Question 31

Ran- GAP stands for, function and molecule type?

Answer 31

• Enzyme: GTPase activating protein
• GTP>GDP
• ran-GDP low affinity for the nuclear import receptor therefore dissociating.
• FORMATION: FREE nuclear import receptor

Question 32

Why does GDP dissociate when the conversion occurs

Answer 32

GDP has lower affinity for the nuclear import receptor, therefore unbinding and releasing it.

free nuclear import receptor

Question 33

Mitocondrial targeting sequences??

Answer 33

terminal mitocondrial
sequencing

again positively charged Amino acids

every four amino acids(positive)

Question 34

Mitochondrial targeting sequences form what type of helix?

Answer 34

Amphipathic helix (pos vs neg) on either side of the helix (protein).

one is hydrophobic and one is hydrophilic

recognised by receptors

Question 35

Location of the mitochondrial targeting sequence

Answer 35

N-terminus

Question 36

Size of mitochondrial targeting sequence

Answer 36

20-80 amino acids

Question 37

How are proteins recognised by mitochondria?

Answer 37

recognised by receptors on the outer membrane

Question 38

TIM and TOM are ?

Answer 38

protein conducting channels

Question 39

TOM

Answer 39

translocator of the outside membrane

Question 40

TIM

Answer 40

Translocator of the inner membrane

Question 41

How are proteins kept from folding? Example ?

Answer 41

Chaperone proteins eg Hsp70

Question 42

TIM requires what ?

Answer 42

membrane potential (negative inside)

ATP hydrolysis- energy

Question 43

In order for proteins to be released from chaperones?

Answer 43

ATP hydrolysis

Question 44

locations in which mitochondria proteins end up?

Answer 44

All compartments of the mito

• intermembrane space
• matrix