Post ER translocation Flashcards
what occurs during vesicle docking
Rab GTPase binds to Rab effector bringing the two membranes close together, v-snare interacts with t snare forming snare complex
V snares need to be recycled ..
NSF (hexametric protein complex), which is a ATPase, and its accessory factor alpha snap break apart cis-snare complex and recycling the v snares
snare complex is a 4 helical bundle
true
trans snare pairing
interaction of snares across two membranes.. after the fusion you get a cis-snare complex
Homotypic fusion
Heterotypic fusion occurs between compartments that don’t differ in composition.
What is heterotypic fusion
Heterotypic fusion occurs between compartments that differ in composition.
give two examples of enzymes that need to stay in the ER ?
enzymes that glycosylate proteins.. enzymes involved in protein sorting
what is KDEL
its a retrieval signal at the C terminus of the protein that is involved in transporting proteins back to the ER from the golgi
why does the KDEL receptor bind to its soluble protein in the cis-golgi but not in the ER ?
because cis golgi has lower ph that ER.. ER more neutral
every time a cop2 vesicle buds it will take a ER membrane protein with it.. how does it return ?
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.
what are the two types of secretion ?
constitutive secretion and regulated secretion… regulated secretion requires an extracellular signal that promotes exocytosis
what happens to proteins in the ER ?
core glycosylation on the asparagine residues of the protein
as the protein travels through the golgi stack..
it is modified.. resulting in a complex oligosaccharide
you can know where the protein is in the golgi by looking at the..
modifications of its sugars
what are the two types of glycosylation ?
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
what are the two models involved in the transport of proteins from one cisterna to the next ?
A) vesicular transport model
B) Cisternal maturation model
describe the lysosome
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
soluble lysosomal resident proteins
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.
if one lacks the enzyme that adds mannose 6-phosphate to the lysosomal hydrolase
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
yeast screens
used to find genes involved in protein trafficking to the vacuole (the yeast lysosome)
the LDL receptor has..
an endocytosis signal..
EGF..
stimulates the cell to divide
