G-Protein Coupled Receptor

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

G-Protein Coupled Receptor

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