Flashcards in vesicular traffic 2 Deck (27):
What are ER exit sites?
specialized site without ribosomes that bud off and takes cargo to intermediate vesicle
How are cargo proteins recognized by COPII?
by exit signals on cargo proteins or their receptors (for soluble proteins)
How does ER resident proteins exit?
by slow leaking
What happens to COPII components after delivering their cargo?
They are recycled and reused
What are some examples for protein receptors that COPII recognize?
ERGIC53 -receptor for blood clotting factors V and VIII lack of these receptors cause excessive bleeding
What happens to misfolded or incompletely assembled proteins?
That are retained by chaperones
What type of signals or the peptide sequences recognized by COPII?
What is homotypic fusion?
ER derived vesicles fusing with one anther to form vesicular tubular clusters (VTC)
What are vesicular tubular clusters?
vesicles carrying cargo to the golgo
What is fusion mediated by?
Tsnares and Vsnares
contributed by both membranes
How does vesicular tubular clusters (VTC) move to the golgi?
What is the retrieval transport of ER?
vesicles that bud off VTC and GA are COPI
What are ER retrieval signals?
signals that COPI bind to retrieve and bring back to the ER
What are some ER retrieval signals?
KKXX - membrane proteins
and a KDEL sequence for soluble proteins
How doe COPI bind to the KKXX membrane protein retrieval signal?
it binds directly to this signal
How does COPI bind to the KDEL soluble protein retrieval signal?
It binds via a KDEL receptor
How is the KDEL soluble protein receptor change for the KDEL sequence?
KDEL receptor has a higher affinity for KDEL sequence at lower (ACIDIC conditions) pH.
KDEL receptor wil be found near the (VTC & GA)
AT neutral PH it has a lower affinity. will be found near the ER
What is kin recognition?
A KDEL independent mechanism for ER boun proteins
they bind to each other
What doe the Golgi apparatus consist of?
4-6 flattened membrane enclosed cisternae
What are the sides of the Golgi apparatus?
cis face (entry face)
trans face (exit face)
with two distinct networks -cis golgi network (intermediate compartment)
trans golgi network (TGN)
Where is the GOLGI located?
near the nucleus and close to the centrosome
localization depends on microtubules
Where does COPI also sort?
Forward from the TGN
Where are oligosacharide chains processed at?
Where are the proteoglycans also initiated at?
What is O linked glycosylation?
adding to the hydroxyl groups of serine and threonine side chains
What is O linked glycosylation catalyzed by?