Bio 201 1st Edition Lecture 16 Outline of Last Lecture I. Signaling ModesII. Ligand- Receptor InteractionsA. Cells ResponseIII. Second MessengersOutline of Current LectureI. GPCR’sA. ExperimentB. How cAMP activates PKAII. GPCR Signal TransductionA. Desensitization B. Tissue SpecificityCurrent LectureI. GPCR’s-The epinephrine receptor is a G-Protein Coupled Receptor. -All GPCR’s contain 7 transmembrane domains. -GPCR’s bind to heterotimer G-proteins -The activation of GPCR’s leads to cAMP production. EpineprhineGDP exchanged for GTP Galpha Galpha-GTP activates Adenylate Cyclase Adenylate Cyclase catalyzes ATP cAMP. But how does cAMP activate glycogen phsosphorylase? A. Experiment- to figure out what combined with cAMP activates glycogen phosphorylase. 1. Inactive glycogen phosphorylase can be activated 2. When radioactive phosphorous is added, enzyme activity is correlated with radioactivity. Protein Kinase A and cAMP activate it. -Protein Kinase A is an enzyme that causes conversion from inactive to active glycogen phosphate.-cAMP activates PKA-Kinases catalyze protein phosphorylation using phosphate from ATP. -Phosphates These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.catalyze dephosphorlyation, phosphorylation reversibility alters conformation and is an extremely common way to regulate protein activity. B. How cAMP Activates PKA 1. Resting: regulatory subunits binds to and inhibit activity of catalytic subunits. 2. Activation: cAMP binds to regulatory subunits dissociation of regulatory and catalytic subunits catalytic subunit activity=PKA. -Cells can respond even when ligand concentrations are low. By high-affinity bonding and signal amplification through enzyme cascades. II. GPCR Signal TransductionA. Desensitization- Cells often desensitize to ligand with continuous exposure. Receptor-mediated endocytosis is just one mechanism for desensitization.B. Tissue Specificity- Different epinephrine receptors activate different pathways (example- intestines vs.
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