Intracellular Protein Trafficking (3)

Question 1

What brings a vesicle closer to the target membrane?

Answer 1

Rab-GTP binds to receptor on vesicle

Rab on membrane binds to Rab-GTP

Question 2

How many t-SNAREs can a v-SNARE bind to and what does this form?

Answer 2

3 t-SNAREs

Forms SNARE complex - 4 alpha-helix bundle

Question 3

Define homotypic fusion

Answer 3

Fusion of same compartment type

Question 4

Define heterotypic fusion

Answer 4

Fusion of different compartment types

Question 5

What breaks the cis-SNARE complex?

Answer 5

NSF ATPase with accessory factor alpha-SNAP

Question 6

What is the recognition sequence for soluble ER proteins moving to the cis-Golgi?

Answer 6

lys-asp-glu-leu - KDEL sequence

Question 7

Which receptors on the cis-Golgi membrane detect vesicles containing soluble ER proteins?

Answer 7

KDEL receptors

Question 8

Why does a soluble protein bind to KDEL receptor in cis-Golgi but not ER?

Answer 8

Lower pH in cis-Golgi than ER

Question 9

What is the transmembrane protein retrieval signal?

Answer 9

lys-lys-X-X

Question 10

What is O-linked glycosylation, where does it occur, and what is it catalysed by?

Answer 10

Sugars added to -OH group of serine/threonine
Golgi apparatus
Multiple glycosyl transferase enzymes

Question 11

What is the role of a lysosome?

Answer 11

Degrades proteins and lipids

Question 12

What marks a protein for translocation from the ER to the lysosome?

Answer 12

Mannose-6-phosphate

Question 13

What is the LDL receptor endocytosis signal?

Answer 13

FDNRVY

Question 14

What is the EGF receptor endocytosis signal?

Answer 14

YXXØ