9-3 Vesicular Transport Flashcards
FISSION vs. FUSION ?
- CargoProtein is selectively separated into budding vesicles and then vesicles PINCH OFF=FISSION
- pinched off vesicle is then trnsported to specific organelles and fuses with them thru their plasma membrane=FUSION
About ___% of proteins made in a cell go to the ER after translation!
About 50% of proteins made in a cell–>to ER!
What are the FIRST steps of Cargo Protein selection & Budding?? [3]
- CArgo Protein is picked up by [cargo-binding receptors] which already have their “foot” stuck inside a vesicles lumen
- Cargo COMPLEX(trget protein + cargo-binding receptr) then changes its cytoplasmic tails so that ADApter proteins can bind
- Inward directed Globular end of Large subunit in CLATHRIN then BINDS to these ADApter proteins and deforms vesicle membrane into a circular transport vesicle!
1: Clathrin-Coat mediates selective (____-____) vesicular transport between the ________, ______ and ______
2: Describe the structure of the Clathrin-Coat
1: Clathrin-Coats mediate selective (Receptor-mediated) Vesicle transport between
TRANS-GOLGI, CELL SURFACE(exocytosis vs. endo) and ENDOSOMES
2:Clathrin= Is a basic unit hexamer AKA “triskilion” tht’s composed of
3 LARGE protein subunits and 3 small protein subunits—>creates a heavy chain——–>multiple Clathrin heavy chains make
Soccer Ball-Clathrin COAT
What is the role of “Dynamin” during vesicle transporting?
2)How does it do this?
3)What happens if Dynamin is blocked?
After Coats have bended vesicle enough to form complete circular vesicle, FINAL PINCHING OFF OF THAT VESICLE FROM MOTHER MEMBRANE is done by DYNAMIN after ATP hydrolysis.
2) ATP hydrolysis tightens Dynamin coils which brings opposite ends of Mother membrane so close together….they fuse up–>pinches off vesicle as a result :-)
3) NO DYNAMIN=NO VESICLE PINCHING OFF
Adapter Proteins in Vesicle transport
2. What are the 4 TYPES of Adapter Proteins
- Binds to Cytosolic part [inside cell] of cargo receptors (which has Trget Cargo Proteins attached) AND {compartment-specific phosphoinositide (PIP) “AKA membrane MARKS” } simultaneously for correct pairing.
- A:(Hrs)=interacts w/PI3P &ubiquitinyltd membrane proteins IN EARLY ENDOSOMES causing the proteins to be retained for delivery to lysosomes
B: (Ap1=adaptor working in trans-Golgi with PI4P membrne mrk ///
C: Ap2=classic adaptor for receptors at plasma membrane…works with PI4,5P )
D: Beta-Arrestin is a Clathrin adapter that contains binding site for AP-2 and thus it directs G-protein coupled receptors(multi-membrane receptors) to clathrin-coated vesicles for endocytosis internalization
COP1 (___ ___ __) transports proteins from the ___to____[_____] AND transports proteins between _______
COP1(Coat Protein Complex) transports proteins from…
(ER <—–Golgi) [RETROGRADE movement] Golgi to ER
AND
COP1 transports proteins BETWEEN GOLGI COMPARTMENTS
1) Describe the ENTIRE process of using SAR1-GTP in order to “recruit” COP2 Coats
2) How does GAP work??
1)SAR1-GEF(brought to ER lumen by correct PIP) converts/activates SAR1-GTPase after converting it from GDP. –>
SAR1-GTPase then goes to Cytosol of transitional ER lumen and MARKS IT for COP2 Coat to come and bind to cargo receptor.
—->Vesicle is pinched off and travels to destination
2)Sec 23/24 GAP works after vesicle has completely formed and coverts SAR1-GTP back to–>GDP=COP2 coat will DISASSEMBLE!
What is the ultimate goal of Phosphoinositides and Rab Proteins?
Helps ensure newly formed freeely floating transport vesicles DOCK and FUSE to correct target membrane
1) What are Phosphoinositides (#1 for vesicle destination targeting)
2) How are Kinases involved?
3) What’s an IMPORTNT function of these regarding Rab-GTPase
1)Guidance device sugars/ “different decorated paint” that wraps around the cytoplasmic side of
ground-level membranes AND transport vesicles which bud from the membranes.
-Specific PI kinases(HIGHLY LOCALIZED TO CERTAIN ORGANELLES) can add specific # of phosphates to these sugars in order to direct it to specific proteins based on its specific phosphate markings
3) [PI3P phosphoinositidol recruits more Rab5-GEF! –>which is an important function for marking a target membrane for destination!]
1)Explain the 2nd way of directing Vesicles after fusion
[with RAB GTPase PROTEINS]
2)explain the positive reinforcing loop that involves PI3P and RabGEF
Rab-GDP when converted to Rab-GTP (by ORGANELLE SPECIFIC
Rab-GEFs) **Rab-GTP pops out hydrophobic parts of itself on vesicle and sticks to specific ground-level membranes using their
Rab-effector fibrils (needed to be recruited with GEF and GTP as well).
2)After Active Rab5-GTP recruits PI3*Kinase –>to make PI3P –>PI3P has ability to recruit more Rab5-GEF–>leads to GEF converting RabGDP into RAB-GTP. More RAB-GTP will deposit onto membrane to recruit more Rab-effector (WITH ADDITION OF PI3P) = membrane will be more heavily marked and BETTER RECOGNIZE incoming vesicle
EACH ____membrane has a specific Rab-_____ which means each organelle membrane has a specific Rab-___ that sticks onto it
EACH ORGANELLE membrane has a SPECIFIC Rab-GEF so this means each organelle membrane has a specific Rab-GTP(activated by GEF) that sticks onto it
What is the TWO roles of COP1 in retrograde transport?? [2]
1.(ARF-GTPase) recuirts COP1 coat to the cis-Golgi in order to RETURN certain resident proteins TO ER that have accidentally traveled over there
OR
2.COP1 helps builder enzymes WITHIN THE GOLGI APPARATUS itself move backward once they’ve advanced/matured a cisterna forward. Moves them backward so they can work to mature the next cisterna forward
What is the role of the Golgi Apparatus in the retention of ER residents?
Golgi App “DISTILLS” the proteins that aren’t supposed to be there and sorts them out so that ARF and COP1 can later come to transport vesicles back to the ER
Identify the components that participates in membrane-vesicle fusion
After Rab-GTP binds to Rab effector fibrils–>V-snare from vesicle and T-snare from ground level target intertwine in a way that gets vesicle sooo close it SPONTANEOUSLY fuses
