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worksheet5mp - Kim Chun Section Thurs 8-8:50...

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Kim Chun Section Thurs 8-8:50 [email protected] BIPN 100, Worksheet 5 G-protein coupled Adenylyl Cylase-cAMP system Receptor-enzyme has two regions: a receptor region on the extracellular side of the cell membrane and an enzyme region on the cytoplasmic side. G-protein coupled receptors have 7 transmembrane helices that are also called serpentine receptors. Enzymes of receptor-enzymes are either protein kinases or guanylyl cyclase (enzyme that converts GTP to cGMP) Has an on/off state: o When GDP is bound, it is in the ____ (on/off) state and the protein is __________(active/inactive). o When GTP is bound, it is in the _____(on/off) state the protein is ________active/inactive. There are two different types of G proteins: Galpha(s): _________ (increases/decreases) the cAMP inside the cell by ____________(activating/inhibiting) adenylyl cyclase Galpha(i)= _________(activates/inhibits) adenylyl cyclase and ____________ (increases/decreases) the amount of cAMP inside the cell. Mechanism of G-protein induced pathway: Adenylyl cyclase= enzyme that converts ATP to second messenger cAMP. cAMP activates _____________, which phosphorylates other intracellular proteins in part of a signal cascade and leads to a cellular response. Main effect of cAMP is to ___________________. Describe the structure of protein kinase A. How does cAMP stimulate protein kinase A? (what happens?) When G protein is activated it can do two things. List them: Methods to turn off signals in G-protein pathway? 1. Original signal (hormone or NT) is removed and metabolizled away and returns receptor to synaptic site and stops activating G-proteins. 2. G-protein GTPase: GTP + H2O GDP + Pi. GDP form is inactive and turns off G proteins. 3. Decrease the receptors by down regulation. a. Less receptors to activate the G-proteins, it can lead to desensitization. Can be done by endocytosis of receptors. 4. Decrease 2 nd messengers with enzymes: a. cAMP phosphodiesterase causes cAMP AMP b. cGMP phosphodiesterase causes cGMP GMP (responsible for penile erection)
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5. Decrease the phosphoprotein (P-Protein): Protein-P + H2O protein + Pi Question: A pharmaceutical company developed several drugs that ineract with the transduction system of a hormone whose receptor is coupled to Gs. For the following, indicate whether the drug will increase or decrease the effects of the hormone, and which step is affected: A. Drug binds to the hormone binding site of the receptor, but doesn’t activate it: B. Drug inhibits GTPase activity of Gs. C. Drug inhibits adenylyl cyclase D. Drug inhibits protein kinase A E. Drug inhibits cAMP phosphodiesterase F. Drug inhibits Protein phosphatases Phospholipase C system Uses Gq that doesn’t interact with adenylyl cyclase, but instead activates _____________: o H-R Gq-GTP Phopholipase C converts PIP2 into DAG or IP3. __________________ nonpolar diglyceride that remains in the lipid portion of the membrane and activates protein kinase C, which phosphorylates proteins.
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