BIO135 G-Protein Notes.txt

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BIO135 G-Protein Notes.txt
2012-05-07 09:28:40
BIO135 Protein

BIO135 G-Protein
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  1. Describe the structure of a G Protein-linked receptor (or G protein-coupled).
    • Seven transmembrane spanning domains.
    • Large cytoplasmic region that associates/activates with trimeric G proteins
  2. Does the GPCR have intrinsic enzymatic activity?
  3. What are 4 classic downstream targets of G Proteins that regulate different effectors?
    • Adenylyl cyclases
    • Phospholipases
    • Ion channels
    • Protein kinases
  4. What are the basic subunits of a G protein?
    alpha, beta, gamma
  5. What about G proteins might explain highly specific responses?
    Different isoforms
  6. What part of the G protein binds with GDP?
    The alpha subunit
  7. When activated, the beta/gamma complex can ___.
    move and activate other targets.
  8. What else provides specific signaling specifity?
    • Cell-specific receptors, G isoforms, and effectors
    • Amount of receptors, G isoforms, and effectors
    • Organization of signaling cascades
    • Accessory proteins
  9. How do accessory proteins regulate G protein action?
    They regulate the strength, efficiency, and specificity of the transmitted signal.
  10. What are some examples of accessory proteins?
    • GAP-43 - promotes GDP dissociation
    • AGS3 - stabilizes G-alpha-GDP interaction
    • Tubulin - directly transfers GTP to G-alpha
  11. What are three types of accessory proteins?
    • Activators of G protein signaling (AGS)
    • Regulator of G protein signaling (RGS)
    • Inhibitors of GDP dissociation
  12. Describe activators of G protein signaling.
    Can activate G proteins without the use of a receptor
  13. Describe regulators of G protein signaling.
    • Accelerate the GTPase activity of specific G-alpha subunits.
    • Quick inactivation - hydrolysis
  14. What is the typical end of a pathway?
    Cell division
  15. What are other roles associated with G proteins?
    • Golgi stability (alternative binding partners)
    • Cell polarity in the fruit fly and nematode
    • Neurite outgrowth and path-finding
  16. What do G protein-linked receptors activate?
    • Adenylyl cyclase
    • Phospholipase C-beta
  17. What effect does the activation of adenylyl cyclase typically have?
    • Increase of cyclic AMP concentration in the cytosol.
    • This rise activates PKA.
    • PKA enters the nucleus and phosphorylates CREB.
    • CREB recruits CBP, and both stimulate gene transcription.
  18. What is produced from the hydrolysis of PIP2?
    • inositol 1,4,5-trisphosphate (IP3) - releases Ca2+ from the ER
    • diacylglycerol (DAG) - helps to activate PKC
  19. Describe how GPCRs increase cytosolic Ca2+ and activate PKC.
    • PLC-beta is activated by G protein (via alpha, beta/gamma, or both).
    • Two messenger molecules, P3 and DAG, produced from hydrolysis of PIP2.
    • IP3 releases Ca2+ from ER
    • Ca2+ and DAG activate PKC
  20. What other purpose does the release of Ca2+ serve?
    Prevents polyspermy by creating fertilization envelope