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76 Cards in this Set

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What family of enzymes is so important in fatty acid metabolism in the ER? What important things can they do?
cytochrome P450 family - including bile acid biosynthesis, cholesterol synthesis, etc.
Why is cytochrome p450 important in pharmacology?
It inactivates many important drugs.
pore in ER membrane that pushes protein through as that protein is made
translocon
What is associated with translocon and ribosome receptor and helps dock it i guess?
CRP receptor.
What arrests the translation of a peptide until it sits on ER membrane (if it has the signal peptide)?
CRP receptor (i think)
For transmembrane proteins, what do they have that makes them clump in translocon of ER,
stop sequence
carboxy terminus of tarnsmembrane is in what in normal?
the cytoplasm. The n terminus is in the lumen of the ER
when you want amino terminus in cytosol for transmembrane spanning proteins, you do what?
have the start sequence in the middle of the protein
What proteins are extremely important in development? Where are they found
GPI-linked proteins. Always in lumen of ER (or on cell surface)
T/F - majority of glycosylation occurs CO-translationally.
true.
What are glycosylated, and what does the glycosylation?
Only asparagines on the proteins are glycosylated, and it comes form a lipid-linked oligosacharide
What is trimmed in glycosylation (in order)
1) first, second, and third glucose individually
2) then you lose 1 manose (THIS marks the end of trimming in ER)
What is the mechansim ensured that only good proteins exit the ER?
ERAD (ER-associated degredation)
What allows the protein, after it is co-translationaly glycosylated, and it has a single glucose on it, to be folded properly?
It binds to calnexin and calreticulin (chaperones that promote folding).
What is the "sensor" of quality control?
the glycosylating enzyme --> UGGT. It acts as folding center to know when protein is correctly folded
What protein helps correctly folded proteins exit the ER?
ERGIC-53
At what point during glycosylation does a protein bind to calnexin and/or calretciulin?q
When 2 of the 3 proteins have been trimmed away.
Once a protien binds to chaperones calnexin and calreticulin, where does it go, to what protein?
ERp57 - which helps it form disulfide bonds
If a protein is misfolded, what reglucosylates it?
glucosyl transferase (of UGGT)
What does ERp57 do?
It is a co-chaperon with calnexin (CNX) and calretciulin (CRT) and accelarates re-fodling and disulfdie bonds
What are glycosylated, and what does the glycosylation?
Only asparagines on the proteins are glycosylated, and it comes form a lipid-linked oligosacharide
What is trimmed in glycosylation (in order)
1) first, second, and third glucose individually
2) then you lose 1 manose (THIS marks the end of trimming in ER)
What is the mechansim ensured that only good proteins exit the ER?
ERAD (ER-associated degredation)
What allows the protein, after it is co-translationaly glycosylated, and it has a single glucose on it, to be folded properly?
It binds to calnexin and calreticulin (chaperones that promote folding).
What is the "sensor" of quality control?
the glycosylating enzyme --> UGGT. It acts as folding center to know when protein is correctly folded
What protein helps correctly folded proteins exit the ER?
ERGIC-53
At what point during glycosylation does a protein bind to calnexin and/or calretciulin?q
When 2 of the 3 proteins have been trimmed away.
Once a protien binds to chaperones calnexin and calreticulin, where does it go, to what protein?
ERp57 - which helps it form disulfide bonds
If a protein is misfolded, what reglucosylates it?
glucosyl transferase (of UGGT)
What does ERp57 do?
It is a co-chaperon with calnexin (CNX) and calretciulin (CRT) and accelarates re-fodling and disulfdie bonds
What trims the last glucose (last of 3) that signals a protein is folded correctly?
Glucosidase II i thinik
How do you get a protein out of ER?
Through ER exit sites (ERES)
how to proteins leave the ER at the exit sites?
Via vesicles with COPII coats
When leaving the ER in COPII coats, where do vesicles go?
to vesicular tubular clusters - where they travel along microtubules
protein pathway in golgi
enter at cis
go through medial
exit at trans
What stage of mitosis does the golig vesiculate?
prophase
what do you remove (sugar wise) in the golgi
cis golgi - you remove mannoses and trim it to 5
later = add glucosmaine
even later - take away more mannose.
didn't get a great understanding of ths
where do O-linked glycosylation occur?
in golgi, on threonines or serines. It is important for connective tissue proteins like GAG's to hold water
for proteolytic processing in golgi, what cleaves positive arginine from albumin?
furin
explain how the mannose 6 phosphate signal works
1) tagged in cis golgi with a phosphate at a mannose residue
2) in TGN, it interacts with specfiic receptor that moves it to late endosomes, which eventually becomes lysosomes
clatherine coats are associated with what?
secretory granules in regulated secretory pathway
Concentration of cargo in vesicles via clathrin that pinches off membrane form WHAT?
secreotry granules that wait to be released
How do you recycle vesicles so the golgi doesn't get huge and the ER doesn't get small?
You get retrograde trafficking.
What part of vesicular transport is very thrmodynamically unfavorable?
fusion of lipid bilayer of vesicles to acceptor compartment.
What proteins are key for budding?
Coat proteins
Arf/Sar
the 3 coated vesicles that control trafficking?
clathrin - secretory granules
copI - recycle membarne back
copII - exit from ER
- these all deform membrane to make bud, and select cargo
What protein families funciton as cargo recpeotrs?
ERGIC-53 family - binds glycosylated cargo
p24 family - not as important, but still importnat
Erv family - least conserved and we know least about
Sar1 and Secs23ect. are what?
the GTPase that is involved in the coating of vesicles.
What are somes disease of Sar1 and Sec?
lose Sar1 - accumulation of chylomicrons in ER
sec23 - collagen trafficking misfunciton. or mutation in e-isoform is differnet disease. This demonstrates taht diff coats trafficks diff vesicles
sec 24 - zebra fish problems, no idea why
How do you cut vesicle off membrane whne it buds off?
Dynamin (of the GTPase family) that spirals around membrane bud and is a "pinchase" that pinches off vesicle
the golig is one what end of microtubles?
minus end (so vesicles move from plus to minus direction) via dyneins that move it in this direciton
intitial recognition of vesicle with target membrane is thru what?
tethers - like velcro, pulls vesicle towards it.
There are tethers in every step of secreotyr pathway
What od tethers work in conjunction with?
Rabs
what is the second layer of recognition
T SNARE in target membarne
V SNARE in vessicle
How many snares come from vesicle/taget membarne?
1 from vesicle
3 from target membrane
bind to recognize vesicle
How do you separate 4-helix bundle of 1 V snare and 3 T snares?
NSF - an ATPase that usesd ATP to dissociate snares so V snares can be recycled back to proximal compartment.
what proteins faciliated fusion of bilayer of vesicle and target membrane ?
predominaetly, it's the snares
the acrosome reaction that allows sperm to penetrate the egg is through what?
the secretory pathwa!
What are the important phospholipids moieties made in the SER?
1)Ethanlamine, serine, and choline are important head groups
2)Sphingosine is precursor to sphingomyelins (brain), and also form glycolipids
3)Galactocerebrosides and ganglioisides are important in development, infection
4)Also cholesterol
What do Cytochorome p450's do?
- important in bile acid biosyntehsis
- lipid biosynthesis
- steroid biosynthesis (from cholesterol precursor)
-vitamin D metablosim
-retinoic acid
-prostacylcins/thrombaxanes A2
What is the most common reaction of cytochrome p450?
A monoxygenase reaction where an oxygen is inserted into organ substrate (RH) while other oxygen is reduced to water
calnexin and clareticulin are located where?
calnexin - lumen of ER
calreticulin - transmembrane in ER
what trims the mannose off in the golgi, and what does it take off exactly?
mannosidase I and II (trim mannnose to 5, and then trimmed to 3
What is used as a marker to track wehre proteins move through the golgi?
endo H (bacterial glycosidase) because the glycogen chain is sensitive to this.
Where does O linked gycoslylation occur?
in golgi, on serine and threonine residues
What is often cleaved from proteins in the golgi due to processing?
Arginine is commonly cleaved in albumin and insulin
explain in detail where lysosome tagging is done?
- proteins are tagged on mannose with a phosphate in the cis golgi
- trans golgi, the M6P receptor interacts with protein and sends it to late endosomes, and eventaully lysosomes
What is dolichol?
a isoprene in the ER membrane that transfers sugar onto proteins i believe
What are the functions of coat proteins?
1) deform membrane to bud off
2) select contents of vesicle
ERGIC-53
transmembrane cargo receptor and a single spanning protein, with an N terminal domain in the ER that binds glyosylated cargo, and the other side (C-terminal?) that binds the coat
The loss of what internal vesicle receptor causes bleeding diseases (?)
ERGIC-53
What is the order of coat binding on cop ii vesicles?
1) Sar, which recruits sec 23-24
2) outer coat binds (sec13-31)
What causes cranio-lenticulo-satural dysplasia?
a mutation in A isofrm of Sec 23, leads to collagen packaging defects and facial abnormalites (the B isoform causes something different).
What energy does dynamin use?
GTPase activity (so GTP)
What does Botox and Tetanus toxin target?
SNARES! That keep synaptic vesicles from fusing
How are snares recycled?
V-snare involved in fusion with COP II vesicles with the cis Golgi are recylcled back to ER in COP I vesicles

V snare invovled in fusing COP I vesicles with the ER is recycled back to golgi in Cop II