Other Structures

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Other Structures
2013-11-11 13:12:27
Cell Bio

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  1. Signal Recognition particle
    - structure
    • Six distinct polypeptides and one RNA molecule= 7S
    • GTP protein (as well as its receptor)
  2. Signal Recognition particle
    - function
    Binds to both ribosome and signal sequence and guides it to an SRP receptor, which will then enable the ribosome to bind to the translocon
  3. Translocon
    • Protein lined channel embedded in the ER membrane
    • Integral membrane proteins
    • thought to have a lateral gate that opens and closes to allow for single-spanning polypeptides to obtain the proper orientation based on solubility
  4. Translocon
    • Allows passage of polypeptide from the ribosome into the ER
    • In inactive state: plugged by a short alpha helix
    • If dealing with a multispanning segment, it can properly orient its transmembrane segments
  5. Translocon
    on the cytosolic side of the RER
  6. Oligosaccharyltransferases
    integral membrane protien
  7. Oligosaccharyltransferases
    adds oligosaccharides to teh polypeptide in the ER
  8. Signal peptidase
    - funciton
    cleave off hte signal peptide from the new polypeptide
  9. ER chaperones
    bind to unfolded or misfolded proteins and give htem a chance to fold correctly
  10. PDI (protein disulfide isomerase)
    • forms and rearranges the disulfide bonds on new polypeptides that were originally cysteine residues in their inactive state
    • -processing enzyme
  11. glycosyltransferase
    Adds sugars to oligosaccharide chains; transfers from a nucleotide sugar to the growing end of the carb chain
  12. Dolichol phosphate
    • Lipid carrier¬† in which the basal segment of each carb chain is assembled on
    • These then get transferred to asparagines residues by oligosaccharyltransferase¬†
  13. Dolichol phosphate
    embedded int he ER membrane by a lipid anchor
  14. Glucosidase II
    Removes any remaining glucose after the gradual modification when two of the three glucose molecules were removed
  15. UGGT
    Conformation-sensing enzyme that recognizes a misfolded or incompletely folded glycoprotein and ads a single glucose residue back to one of the mannose residues; allows rhe ER chaperone to recognize it
  16. BiP
    molecular chaperone
  17. BiP
    keeps the sensors that detect misfolded proteins in an inactive state
  18. Sialyltransferase
    • Adds sialic acid to the terminal position of the chain
  19. Sialyltransferase
    in the trans face of the Golgi
  20. Sar1
    GTP protein
  21. Sar1
    • When activated, it inserts its N-terminal into the lipid bilayer, causing bending
    • Also plays a regulatory role
    • Initiates vesicle formation and regulates assembly of the vesicle coat
  22. KDEL receptor
    integral membrane protein
  23. KDEL receptor
    Shuttles between the cis Golgi and ER compartments, recognizing and returning proteins of the ER
  24. GGAs
    • Contain several domains, each capable of grasping a different protein involved in vesicle formation
  25. GGAs
    • Outer ends bind to clathrin, holding the clathrin scaffolding onto the surface of the vesicles
  26. Arf1
    GTP-binding protein
  27. Arf1
    • Sets the stage for the binding of other coat proteins to clathrin-coated vesicles
    • It extends a membrane-bending alpha helix that acts in conjunction with the clathrin coat to initiate budding of the vesicle
  28. Rab
    G proteins that bind to membranes by a lipid anchor
  29. Rab
    Membrane trafficking and vesicle targeting; also deals with recruiting proteins involved in membrane trafficking like motor proteins
  30. SNAREs
    • Contains a SNARE motif that allows binding to other SNARE motifs on other membranes
    • v-snares: become incorporated into membranes of transport vesicles during budding
    • t-snares: located in membranes of target compartments
  31. SNAREs
    Proteins that engage in the docking interactions, where the cytosolic regions of integral proteins of two membranes interact