Subcellular trafficking

Question 1

What is responsible for the movement of vesicles and organelles around cells?How does it work?

Answer 1

Motor proteins - enzymes that convert chemical energy into mechanical energy- helps to move proteins around the cell as the hydrolysis of ATP induces conformational changes in the protein that move the motor protein along its designated track

Question 2

processive vs non-processive motors:

Answer 2

processive motors stay always attached along the track
non processive - will detach

Question 3

name 3 features of kinesines that are similar to myosins:

Answer 3

the 3 domains - head, neck, tail

Question 4

what does cytosolic mean?

Answer 4

membrane bound vesicles are transported by their own specific kinesins along route

Question 5

how do kinesins help during cell division?

Answer 5

spindle assembly and chromosome segregation

Question 6

name and explain the 2 classes of dyneins:

Answer 6

cystosolic - movement of vesicles/chromosomes, largest and fastest , motor protein
axonemal - beating of cilia and flage;;a

Question 7

what are conventional kinesins?

Answer 7

are positive-ended motors that always move to the positive end of the microtubules

Question 8

Explain polypeptide synthesis:

Answer 8

1. signal proteins are bound by the SRP, causing a pause in translation
2. membrane proteins are glycosylated as the polypeptide chain is translated and threaded through the translocator in the ER membrane

Question 9

What does localisation to membrane-bound compartments enable?

Answer 9

• controls interactions between proteins
• • allows regulation of the local environemtns
• • protects the microenvironments from toxins

Question 10

Name 3 mechanism for exchanging materials between organelles:

Answer 10

1- gated transported through pore complexes
2- transmembrane transport involves direct passage across an intact membrane
3-vesicular transport- fusion of the membrane

Question 11

What are FG nups?

Answer 11

unstructured , form the seive- form a structured mesh that functions as a hydrogel

Question 12

What are importins?

Answer 12

importin alpha recognises NLS on cargo proteins
importin beta interacts with the pore complex via FG nups within the NPS

Question 13

Explain the RANGTP cycle:

Answer 13

1. RANGTP binds to importin beta to release the cargo
2. active movement transports the cargo into the nucleuus, RANGTP is rephosphorylated to restart the cycle

Question 14

What is STAT1 and NFAT1?

Answer 14

STAT1- important transcription factor which is an important mediator of the innane immune response
NFAT1 - important transcription factor and an important mediator of T-cell activatation

Question 15

How does the main export factor of nuclear export work?

Answer 15

NXF1 binds to TRP at the NPC basket without utilising the RANGTP gradient, to provide directionality

Question 16

Name 3 actin based motilities:

Answer 16

• nucleation of new actin filaments = overcomes initial inactivation barrier
• capping of older filaments = capping protein,
• recycling of monomers from old filaments= only certain amounts of actin that can be used for ADP

Question 17

filopedia vs lamellipodia

Answer 17

filopedia - finger like protrusions from the cell membrane, used in sesing the environments- formedd from actin polymerisation
lamellipodia - thin, sheet-like protrusions of the membrane at the front of the cell= meshwork of unbundled actin filaments

Question 18

How does cell motility work?

Answer 18

formation of new adhesion via integrins and new stress fibres, traction is generated by adhesion, proteases degrade contacts

Question 19

What is proteolysis?

Answer 19

breakdown of proteins into polypeptides/amino acids

Question 20

What is ubiquitin- mediated proteolysis good for?

Answer 20

• quality control
• recycling of peptides/amino acids
• destructs mutant proteins

Question 21

What happens to polyubiquitylated proteins with K11/K48 ubiquitin linkages?

Answer 21

recognised by the 26S protein and degraded- activated by ATP, the proteins form ester linkages

Question 22

what’s the importance of E3 linkages?

Answer 22

• protein polyubiquitylation is controlled by the diversity of E3 ubiquitin layers
• dysregulation of E3 ubiquitin ligases leads to disease

Question 23

Explain the component 20S which is found in the proteosome core:

Answer 23

barrel-like,2 copies of each 14 distincts subunits
B1- cleaves after acidic residues
B2 - cleaves after basic residues
B5 - cleaves after hydrophobic residues

Question 24

explain the 19S component of the 26S component

Answer 24

• base and lid components -regulates functions within the proteosome

Question 25

what is the role of the ubiquitin-proteosome pathway?

Answer 25

- cell growth - dna damage and repair - transcription - metabolism