Ubiquitination

Question 1

Ub

Answer 1

• prevents surfaces recognised by various Ub binding proteins

Question 2

Ubiquitin cascade

Answer 2

1) Ub C-terminus Gly binds to E1 active site Cys by thioester bond
2) binds to E2 AS Cys via transthiolation
3) binds to lysine epsilon-amine via isopeptide linkage

Question 3

19S RP

Answer 3

• closed in free state
• Rpn10, 13: Ub-receptors
• Rpn1, 2: scaffold proteins, secondary Ub-binding sites
• Rpn11 = DUB
• heterohexameric clamp brace

Question 4

20S CP

Answer 4

• rapid degradation, limiting specificity
• multiple ASs

Question 5

How does the substrate enter the axial pore?

Answer 5

conserved loops project from ATPase to unfold it

Question 6

s1

Answer 6

• Rpn11 offset from pore
• disordered substrate region attached to ATPase (+ bound by receptor)
• ATPase and core not aligned; gate = closed

Question 7

s4

Answer 7

• Rpn11 aligned: DUB
• ATPase and core aligned

Question 8

Ub-independent proteins

Answer 8

recognised by 26SP directly

Question 9

ERAD-T

Answer 9

translocon

Question 10

ERAD-M

Answer 10

membrane

Question 11

ERAD-L

Answer 11

lumen

Question 12

cdc48

Answer 12

• cytosolic retrotranslocon: ERAD-C
• AAA-ATPase

Question 13

MAD and

Answer 13

CHLORAD

Question 14

UBLs

Answer 14

• 20 in Eukarya
• fewer substrates
• less E2s and E3s
• AT8 and 12

Question 15

SUMOylation

Answer 15

• SUMO-targeted Ub-ligases compete for acceptor lysines
• change protein stability, activity and sub cellular localisation

Question 16

SUMOylation function

Answer 16

• peri-telomeric heterochromatin
• syncytial cleavage
• Hh signalling

Question 17

SUMOylation and Hh signalling

Answer 17

• E2 (Ubc9) KO interferes with “smoothened” receptors; developmental defects