904-921 G protein coupled receptors

904-921 G protein coupled receptors - SIGNALING THROUGH...

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SIGNALING THROUGH G-PROTEIN-COUPLED CELL-SURFACE RECEPTORS AND SMALL INTRACELLULAR MEDIATORS Trimeric G proteins relay signals from GPCRs o When an extracellular signal molecule binds to a GPCR, the receptor changes so that it can activate a G protein o G proteins are made of alpha, beta and gamma subunits o In unstimulated state, alpha subunit has GDP bound and the G protein is inactive o When GPCR is activated, it induces the alpha subunit to release its bound GDP, allowing GTP to replace it o This activates the G protein o Regulator of G protein signaling (RGS) proteins act as alpha-subunit-specific GTPase-activating proteins and they help shut off G-protein mediated responses in eucaryotes Some G proteins regulate the production of cyclic AMP o Cyclic AMP is a small intracellular mediator o Cyclic AMP is made from ATP by enzyme called adenylyl cyclase o Cyclic AMP is destroyed by cyclic AMP phosphodiesterases o GPCRs that increase cyclic AMP are coupled to a stimulatory G protein, which activates adenylyl cyclase and thereby increases cyclic AMP concentration
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This note was uploaded on 12/30/2010 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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904-921 G protein coupled receptors - SIGNALING THROUGH...

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