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G-Protein Coupled Receptor

G-Protein Coupled Receptor

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G-PROTEIN COUPLED RECEPTORS
  • All eukaryotes have
  • Act indirectly on a separate protein (enzyme or ion channel)
  • Trimeric GTP-binding protein (G-protein) mediates this interaction
  • Same signal molecule can activate multiple different receptors
STRUCTURE
Receptor
  • Seven transmembrane segments (hallmark)
G-protein
  • Trimeric (alpha, beta, gamma subunits)
  • Alpha and Gamma subunits have small lipid molecules that anchor them to inner layer of plasma membrane
  • GTPase binding domain
    • GDP - Inactive state
    • GTP - Active state
ACTIVATION STEPS 1) Signal molecule binds to receptor 2) Receptor undergoes conformational change 3) Alpha subunit kicks out GDP and binds GTP 4) Alpha subunit becomes activated as does beta/gamma complex 5) Activated units activate other proteins in the signaling pathway 6) Eventually GTP hydrolyzed into GDP and the G-protein becomes inactive
PHARMACOLOGIC CORRELATION
  • About half of all known drugs target G-protein coupled receptors or some part of a G-protein coupled receptor pathway

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