G-Protein Coupled Receptors Overview
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Questions and Answers

What occurs when an extracellular signal molecule binds to a GPCR?

  • The G-protein remains inactive with GDP bound.
  • The receptor undergoes a conformational change activating the G-protein. (correct)
  • The G-protein binds directly to the ion channels in the membrane.
  • The G-protein immediately hydrolyzes GTP to GDP.

    • Which component of the G-protein is involved in the exchange of GDP for GTP?

  • Alpha subunit (correct)
  • G-protein-coupling receptor
  • Beta subunit
  • Gamma subunit

    • How does RGS regulate G-protein signaling?

  • By stabilizing the G-protein in its active form.
  • By activating the GTPase activity of the alpha subunit. (correct)
  • By acting as a guanine nucleotide exchange factor.
  • By increasing the exchange rate of GDP for GTP.

    • What is the significance of GTP hydrolysis in the function of G-proteins?

    <p>It inactivates the G-protein and resets the signaling pathway.</p> Signup and view all the answers

    What characteristic of GPCRs allows them to activate different types of G-proteins?

    <p>The specific conformational changes they undergo upon ligand binding.</p> Signup and view all the answers

    Study Notes

    G-protein Coupled Receptor (GPCR)

    • GPCRs are membrane-bound proteins that bind to signaling molecules, initiating a cascade of events within the cell.
    • The binding of an extracellular signaling molecule causes a conformational change in the GPCR, allowing it to activate a GTP-binding protein (G-protein).
    • These receptors thread through the cell membrane seven times, with the N-terminus located outside the cell and the C-terminus inside the cell.

    G-Protein Structure and Activation

    • G-proteins are heterotrimeric, meaning they consist of three subunits: alpha, beta, and gamma.
    • In their inactive state, G-proteins have GDP bound to the alpha subunit.
    • Upon signal molecule binding to the GPCR, the alpha subunit's affinity for GDP decreases, allowing GTP to bind in its place.
    • This binding event causes the alpha subunit to detach from the beta and gamma subunits, activating the G-protein.
    • Activated alpha and beta/gamma subunits interact with target proteins, such as enzymes or ion channels, to trigger cellular responses.

    G-Protein Deactivation and Regulation

    • The alpha subunit possesses GTPase activity, meaning it can hydrolyze GTP back to GDP.
    • This GTP hydrolysis returns the alpha subunit to its inactive conformation, allowing it to reassociate with the beta/gamma subunits.
    • GTPase activity is enhanced by the binding of the alpha subunit to target proteins or RGS proteins.
    • RGS proteins are specific regulators of G-protein signaling and act as GTPase activating proteins (GAPs), accelerating the GTP hydrolysis process.
    • This rapid deactivation of G-proteins ensures a precise and controlled cellular response.

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    G-protein Coupled Receptor (GPCR) Summary PDF

    Description

    This quiz covers the fundamentals of G-protein coupled receptors (GPCRs) and their activation. Participants will explore the structure of GPCRs and G-proteins, along with the mechanisms by which these receptors interact with signaling molecules. Test your understanding of cellular signaling pathways and the role of GPCRs in biological processes.

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