Trafficking Pathways

Question 1

Vesicular organs

Answer 1

ER, golgi, lysosomes, endosomes

Question 2

Three domains of ER

Answer 2

Smooth-lipid metabolism
ROUGH-ribosomes
ERGIC- vesicles exit to golgi

Question 3

Translation of free ribosomes in cytosol. Proteins go to

Answer 3

Cytosolic pathway.

Nucleus, peroxisomes, mitochondria, chloroplasts

Question 4

Translation at membrane bound ribosomes

Answer 4

Secretory pathways. Golgi, plasma membrane, endosomes, lysosomes, nuclear membrane, secretory vesicles, peroxisome membrane

Question 5

Cotranslational translocation

Answer 5

Proteins synthesized in membrane bound ribosomes enter ER during translation
SRP binds pausing translation, complex brings it to RER (SRP released), ribosome binds translocon and it opens, translation resumes and translocated across membrane

Question 6

Post translational translocation

Answer 6

Proteins translated on free ribosomes move into ER after translation
Protein translated and HSP 70 and 40 maintain unfolded, bring to ER where recognized by Sec 62/63 and is inserted thru translocon, BiP drives protein inside and uses ATP for proper folding

Question 7

What determines domain topology

Answer 7

Position of signal sequence

Question 8

BiP

Answer 8

Chaperone, binds to unfolded polypeptide and mediates folding

Question 9

Protein disulfide isomerase

Answer 9

Facilitates disulfide bind formation

Question 10

N-linked glycosylation

Answer 10

Oligosaccharide (NAG and mannose) synthesized on lipid (dolichol) carrier and prevents protein aggregation in ER. Sorting signal
-modified in Golgi from just mannose and NAG to several different oligosaccharides (fucose, galactose, Sialic Acid)

Question 11

GPI anchors

Answer 11

Glycolipids assembled in ER membrane added to C terminus. Lipidation

Question 12

KDEL/KKXX

Answer 12

C terminus target sequence signals to go back to ER. Recognized in ERGIC. Ex: BiP

Question 13

Golgi function

Answer 13

-proteins from ER are processed and sorted
-transport to endosomes, lysomes, plasma membrane, secretion
-synthesize glycolipids and sphingomyelin
4 regions

Question 14

Stable cisternae model

Answer 14

Transport vesicles carry proteins between cisternae for protein movement in golgi

Question 15

Cisternal maturation model

Answer 15

Proteins carried within cisternae which gradually mature and progressively move through golgi in cis to trans direction

Question 16

N-linked oligosaccharides of lysosomal proteins

Answer 16

Modified by mannose phosphorylation using UDP. Recognized by mannose-6-phosphate receptor in trans golgi network, which transports them to endosomes then lysosomes

Question 17

O linked glycosylation

Answer 17

Carbohydrates added to side chains of serine and threonine in golgi. Makes proteoglycans, can be further modified by addition of sulfate groups

Question 18

3 ways transport form golgi to cell surface can occur

Answer 18

Direct transport to plasma membrane, recycling endosomes, regulated secretory pathways (granules)

Question 19

Hormones and neurotransmitters

Answer 19

Aggregate in trans golgi network and are packaged into secretory granules until signals direct their fusion with plasma membrane

Question 20

COPII coated vesicles

Answer 20

Carry proteins from ER to ERGIC and onto golgi

Question 21

COPI coated vesicles

Answer 21

Bud from ERGIC or golgi and carry their cargo back to earlier compartments

Question 22

Clatherin coated vesicles

Answer 22

Both directions between the trans golgi network, endosomes, lysosomes, plasma membrane

Question 23

Formation of coated vesicles regulated by

Answer 23

Small GTP binding proteins (ARF1 and Sar1).

Uses GEF for GDP to GTP, adds adapter, cargo and coat

Question 24

Interaction between transport vesicles and target membranes mediated by

Answer 24

Tethering factors and small GTP binding proteins (Rab)

Question 25

SNAREs

Answer 25

Drives membrane fusion. Has coiled coil domain and binds to other coiled coils. Brings 2 membranes in direct contact and leads to fusion.
Tethering factors binding coat proteins initiates this