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341lecture31nov25sakai - Cell Biology 341 Last lecture Weds...

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Cell Biology 341 Weds., November 25, 2009 Today: Target proteins in G-protein pathways that activate enzymes or ion channels You may omit pages 931-936 of the reading, but see figures 15- 61, 66 and 67 No office hours on Tues, Dec 1 Office hours will be Thursday, Dec 3, from 1-3 pm Last lecture: The gas NO causes blood vessel dilation by activating guanylyl cyclase → cGMP Plasma membrane receptors bind hydrophilic signals G-protein-coupled receptors are 7-span transmembrane proteins When activated, G-protein-coupled receptors trimeric G-protein activation by nucleotide exchange on α subunit (GTP replaces GDP) Amplification occurs because a single activated receptor can activate many G-protein molecules Activated α-GTP and/or activated βγ activation of target protein inactivation by α GTP hydrolysis within seconds The α subunit of G s activates adenylyl cyclase cAMP
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Some G proteins regulate the production of cyclic AMP (cAMP) epinephrine (adrenaline) binds a G- protein-coupled receptor that activates the stimulatory G-protein G s The activated α subunit of G s activates the enzyme adenylyl cyclase This plasma membrane-bound enzyme synthesizes cAMP from ATP cAMP is an active
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