Post ER translocation

Question 1

what occurs during vesicle docking

Answer 1

Rab GTPase binds to Rab effector bringing the two membranes close together, v-snare interacts with t snare forming snare complex

Question 2

V snares need to be recycled ..

Answer 2

NSF (hexametric protein complex), which is a ATPase, and its accessory factor alpha snap break apart cis-snare complex and recycling the v snares

Question 3

snare complex is a 4 helical bundle

Answer 3

true

Question 4

trans snare pairing

Answer 4

interaction of snares across two membranes.. after the fusion you get a cis-snare complex

Question 5

Homotypic fusion

Answer 5

Heterotypic fusion occurs between compartments that don’t differ in composition.

Question 6

What is heterotypic fusion

Answer 6

Heterotypic fusion occurs between compartments that differ in composition.

Question 7

give two examples of enzymes that need to stay in the ER ?

Answer 7

enzymes that glycosylate proteins.. enzymes involved in protein sorting

Question 8

what is KDEL

Answer 8

its a retrieval signal at the C terminus of the protein that is involved in transporting proteins back to the ER from the golgi

Question 9

why does the KDEL receptor bind to its soluble protein in the cis-golgi but not in the ER ?

Answer 9

because cis golgi has lower ph that ER.. ER more neutral

Question 10

every time a cop2 vesicle buds it will take a ER membrane protein with it.. how does it return ?

Answer 10

LYS-LYS-X-X is a retrieval signal at the C terminus of the ER membrane protein.. it recognised by the proteins of the COP1 coat. And so, the COP1 coat concentrates the protein in the vesicle and transfers the protein back to the ER.

Question 11

what are the two types of secretion ?

Answer 11

constitutive secretion and regulated secretion… regulated secretion requires an extracellular signal that promotes exocytosis

Question 12

what happens to proteins in the ER ?

Answer 12

core glycosylation on the asparagine residues of the protein

Question 13

as the protein travels through the golgi stack..

Answer 13

it is modified.. resulting in a complex oligosaccharide

Question 14

you can know where the protein is in the golgi by looking at the..

Answer 14

modifications of its sugars

Question 15

what are the two types of glycosylation ?

Answer 15

core glycosylation on the asparagine residues of the protein in the ER .. and O-linked glycosylation. This involves sugars added to -OH groups of serine or threonine catalysed by a series of glycosyl transferase enzymes in the golgi

Question 16

what are the two models involved in the transport of proteins from one cisterna to the next ?

Answer 16

A) vesicular transport model

B) Cisternal maturation model

Question 17

describe the lysosome

Answer 17

contains proteases and lipase for degrading proteins and lipids.. can be considered a concentrated bag of enzymes .. fuses directly with the late endosome and is then reformed.. the lumen is acidic. its the end point of the endocytic pathway. most acidic organelle in the cell

Question 18

soluble lysosomal resident proteins

Answer 18

Mannose 6-phosphate added to the lysosomal hydrolase in the cis-Golgi which acts as a transport signal and will takes to trans golgi network.. its is then recognised by a mannose 6 phosphate receptor, which concentrates the protein in clathrin coated vesicles….. by means of the vesicular transport, the protein will then be transported to a late endosome. The receptor dissociates from the protein at acidic pH. The late endosome then fuses with lysosome.. and so the the protein ultimately ends up in the lysosome, where it is activated due to the low pH environment in the lysosome.

Question 19

if one lacks the enzyme that adds mannose 6-phosphate to the lysosomal hydrolase

Answer 19

lysosomal hydrolase molecules are not transported to the lysosome because they are not recognised by the mannose 6 phosphate receptors; instead the enzymes are secreted from the cell. this results in mucolipodosis type 2 or l-cell disease

Question 20

yeast screens

Answer 20

used to find genes involved in protein trafficking to the vacuole (the yeast lysosome)

Question 21

the LDL receptor has..

Answer 21

an endocytosis signal..

Question 22

EGF..

Answer 22

stimulates the cell to divide