Vesicular Traficking II (Lecture 15) Flashcards
The ______ pathway goes from the ER to the cell surface
Secretory
The ______ pathway goes from the cell surface back to the ER.
Endocytic
The first step in the secretory pathway is mediated by ______ vesicles.
COPII
True or False: In the secretory pathway, they vesicles contain newly synthesized proteins destined for Golgi, cell surface, or lysosomes.
True
True or False: In the secretory pathway, vesicles contain t-SNARE components.
False, v-SNARE
The secretory pathway moves in the ______ direction.
Anterograde
v-SNARE recycling and retrieval of missorted ER-resident proteins from the cis-Golgi is via ______-coated vesicles in the ______ direction
COPI, retrograde
How do formation of class B sec mutants occur in yeast cells?
Triggered when Sec12 catalyzes activation of cytosolic Sar1
What mutant class has accumulation in the cytosol and doesn’t function to transport into the ER.
Class A
What class doesn’t allow budding of vesicles from the rough ER and causes accumulation in the rough ER.
Class B
What class causes accumulation in the Golgi and inhibits transport from Golgi to secretory vesicles
Class D
What is the fate of secretory proteins and defective function for Class E
Accumulation in the secretory vesicles, transport from secretory cells to cell surface
What is the fate of secretory proteins and defective function for Class C
Accumulation in the ER-to-Golgi transport vesicles, fusion of transport vesicles with Golgi
True or False: Sec24 interaction with cytosolic domain di-acidic targeting signal (purple) recruits cargo protein into the vesicle membrane.
True
True or False: Some integral ER membrane proteins are targeted to COPII vesicles for transport to Golgi.
True
What type of sorting signal is used for protein targeting to COPII for cytosolic domains?
Di-acidic sorting signal
True or False: The di-acidic sorting signal binds to the Sec23 complex.
False, Sec 24 complex
True or False: Certain integral ER membrane proteins also bind cargo proteins in the lumen via the exoplasmic domain
True
______ acts as a cargo receptor for collagen; simultaneously binds collagen and ______ on opposite sides of the membrane.
TANGO1, Sec24
True or False: Other sorting signals exist but can bind to either Sec24, Sec23, and Sar1.
False, only Sec24
True or False: Many vesicles move by diffusion for small distances.
True
How do vesicles travel long distances?
Use microtubules as railroad tracks
True or False: In ER - resident proteins, many of the soluble proteins assist in folding and modification of newly synthesized secretory proteins.
True
What are 2 examples of soluble proteins that assit in folding modification?
chaperone BiP, protein disulfide isomerase
What happens when soluble proteins accidently enter COPII vesicles?
COPI recycles these back so they do not become depleted
True or False: Most soluble proteins carry a KDEL sequence at the N terminus.
False, C-terminus
What does KDEL stand for?
Lys-Asp-Glu-Leu
What is KDEL necessary for?
localize a protein to the ER
True or False: KDEL receptor acts mainly to retrieve soluble proteins containing the KDEL sorting signal
True
True or False: The KDEL receptor binds at high pH.
False, low pH
True or False: The KDEL receptor is found mainly in the ER.
False, Found mainly in transport vesicles
True or False: In the KDEL receptor, the differing pH in Golgi vs ER mediates peptide binding or release.
True
KDEL receptor contains _____ sorting signal at the very end of the C-terminal segment (cytosolic).
KKXX (X stands for any amino acid)
True or False: KKXX signal binds to a complex of COPII subunits to incorporate membrane proteins into COPII vesicles.
True
Other the the KDEL receptor, what other sequence can target certain proteins to COPI vesicles?
Di-arginine
True or False: The DI-arginine sequence does not have to occur at the C terminus.
True
Cisternal maturation is responsible for ______ transport.
Anterograde
Vesicle-based transport visible by electron microscopy are all ______ transporters.
COPI (retrograde)
How does retrograde transport effect the makeup of the Cisternal lumen?
medial-Golgi is gaining trans-Golgi enzymes, and losing medial-Golgi enzymes to the cis-Golgi
therefore, medial-Golgi thus progressively becomes the new trans-Golgi compartment, through cisternal maturation
______ -coated vesicles transport newly synthesized proteins containing Golgitargeting sequences in their cytosolic domain or bound to such proteins from the rough ER to the cis-Golgi (anterograde direction)
COPII
______-coated vesicles transport vesicles carrying ER/Golgi-resident proteins in the retrograde direction, which supports Golgi cisternal maturation
COPI
______-coated vesicles transport proteins from the plasma membrane (cell surface) and thetrans-Golgi network to late endosomes
Clathrin
What GTP-binding protein is in COPI, COPII, and Clathrin coated proteins?
ARF protein in COPI and clathrin-coated vesicles
Sar1 protein in COPII vesicles
