Exam 3: RR (9)

  1. I.                   Targeting Vesicles to a Particular Component
    a.      vesicle fusion requires specific __between different membranes
                                                                  i.      vesicles from __fuse with __
    b.      __ is one of the factors that ensures a directed flow through the membranous compartments of the cell
    c.       it is thought that a vesicle contains __ associated with its membrane that govern the __ and __ of that vesicle
    • interactions 
    • ER 
    • cis Golgi network (ERGIC)
    • selective fusion
    • specific proteins
    • movements and fusion potential
  2. Steps:
    • i. movement of the vesicle toward the specific target compartment
    • ii. tethering vesicles to the target compartment
    • iii. Docking vesicles to the target compartment
    • iv. Fusion between vesicle and target membranes
  3. Step One: movmeent

    1.      membranous vesicles must move far distances through the __before reaching their eventual __
    a.      mediated by __, which carry cargo containers along __
    • cytoplasm 
    • target
    • microtubules
    • defined pathways
  4. Step Two: tethering
     i.      tethering vesicles to the target compartment
    the initial contacts between a transport vesicle and its target membrane, such as the Golgi cisternae, are thought to be mediated by a diverse collection of “__” proteins

    Two groups: 
    • tethering
    • rod-shaped, fibrous proteins and large multiprotein complexes that appear to hold the two membranes in closer proximity
  5. a.      different __ initiate __between different types of membranes
                                                                                                                                          i.      ex: __act in and around the Golgi complex and may serve as __to __ and __ carrying __
    • tethering proteins
    • fusion 
    • golgins 
    • tentacles 
    • reach out
    • capture transport vesicles
    • Golgi-bound cargo
  6. 1.      much of the specific between vesicle and target may be conferred by a family of small __ called __, which cycle between an __ and an __

    a.      __ associate with membranes by a __
    • G proteins
    • Rabs
    • active GTP-bound state
    • inactive GDP-bound state
    • GTP-bound Rabs
    • lipid anchor
  7.                                                                                                                                       i.      with over sixty different __genes identified, these proteins constitute the most diverse group of proteins involved in __
                                                                                                                                        ii.      more importantly, different Rabs becomes associated with different membrane compartments
    • Rab 
    • membrane trafficking
  8. 1.      this __ gives each compartment a unique __, which is required to do what?
                                                                                                                                        ii.      In their __ state, __play a key role in __ by recruiting specific __ to specific membrane surfaces
    • preferential localization
    • surface identity
    • recruit the proteins involved in targeting specificity
    • GTP-bound

    • Rabs 
    • vesicle targeting
    • cytosolic tethering proteins
  9. 1.      __also play a key role in __ involved in other aspects of __, including the __ that move membranous vesicles through the cytoplasm
    • Rabs 
    • recruiting numerous proteins
    • membrane trafficking
    • motor proteins
  10. Step Three: Docking                                                     

    1.      at some point during the process leading to vesicle fusion, the membranes of the vesicle and target compartment come into close contact with one another as the result of __
    an interaction between the cytosolic regions of integral proteins of the two membranes
  11. a.      the key proteins that engage in these interactions are called __, and they constitute a family of more than __ whose membranes are localized to specific __
    • SNAREs
    • 35 membrane proteins
    • subcellular compartments
  12. 1.      Althouh __vary considerably in structures and size, all contain a segment in their cytosolic domain called a __ that consist of __ capable of forming a complex with another __

    • SNAREs 
    • SNARE motif
    • 60-70 amino acids

    SNARE motif
  13. Snares are divided into __ and __. Explain them.
    •                                                                                                                                       i.      v: become incorporated into membranes of transport vesicles during budding
    •                                                                                                                                     ii.      t: located in the membranes of target compartments
  14. 1.      best studied __are those that mediate __ with the __membrane during the regulated release of __
    a.      in this case, the __ of the __ contains two__, which are __ and __, whereas the __vesicle membrane contains a single __, __
    • SNAREs 
    • docking of synaptic vesicles
    • presynaptic 
    • neurotransmitters
    • plasma membrane
    • nerve cell
    •  t-SNAREs, syntaxin and SNAP-25
    • synaptic 
    • v-SNARE, synaptobrevin
  15.                                                                                                                                       i.      as the __vesicle and __membrane approach one another, the __motifs of __ and __ molecules from apposing membranes interact to form __
    1.      each bundle consists of __, two donated by __ and one each donated by __ and __
    • synaptic 
    • presynaptic 
    • SNARE 
    • t- and v-SNARE
    • four-stranded bundles
    • four alpha helices
    • SNAP-25
    • syntaxin and synaptobrevin
  16. a.      these parallel __ zip together to form a tightly interwoven complex that pulls the two apposing lipid bilayers into very close association
                                                                                                                                                                                                                  i.      the formation of similar __ bundles occurs among other __at other sites throughout the cell, wherever membranes are destined to fuse
    • alpha helices
    • four-stranded helical
    • SNAREs
  17. a.      the __of the __and the __membrane are targets of two of the most potent bacterial toxins; they act as __whose only known substrates are __
                                                                                                                                          i.      cleavage of the __ by the toxins block the release of __, causing __
    • SNAREs 
    • synaptic vesicle 
    • presynaptic 
    • proteases 
    • SNAREs
    • neuromal SNAREs
    • neurotransmitters
    • paralysis
  18. Step Four: Fusion
     1.      when artificial lipid vesicles containing purified__ are mixed with liposomes containing purified__, the two types of vesicles fuse with one another, but not with themselves
    2.      interaction between __ and __ are capable of pulling two lipid bilayers together with sufficient force to cause them to __
    • t-SNAREs
    •  v-SNAREs,
    • t- and v-SNAREs

  19. a.      however, a large body of evidence suggests that, although interaction between v- and t- SNAREs is required for membrane fusion, it is not sufficient by itself to bring about __within a cell 
  20. 1.      the four-stranded __bundle remains locked in an __state by interaction with __proteins
    a.      vesicles at this stage remain __at the membrane and ready to __their conents almost instantaneously once they receive an __, in the form of a rise in __
    • SNARE 
    • arrested 
    • accessory 
    • docked 
    • discharge 
    • activating signal
    • Ca2+ concentration
  21.                                                                                                                                       i.      regardless of how it is regulated, ocne the lipid bilayers of the two membranes merge, the __that previously projected from separate membranes now __
    1.      __of the __ is achieved by a doughnut-shaped, cytosolic protein called __that attachs to the __bundle and, using energy from ATP hydrolysis, twists it apart

    reside in the same membrane


    • four-stranded SNARE complex
    • NSF 
    • SNARE
  22. ANSWER to how vesicles specificity is determined: the ability of a particular vesicle and target membrane to fuse is determined by  ???????????
    the specific combination of interacting proteins, including tethering proteins, Rabs, and SNAREs that can be assembled at that site in the cell
  23.                                                               i.      taken together, these multiple interactions between several types of proteins provide a high level of __, ensuring that each membrane compartment can be c__
    • specificity
    • selectively recognized
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Exam 3: RR (9)