Problem Set 6 Q&A

Problem Set 6 - Problem Set 6 1 List six steps of signal transduction from ligand to downstream target Which steps amplify the signal Ligand

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Problem Set 6 1) List six steps of signal transduction from ligand to downstream target. Which steps amplify the signal. Ligand Receptor G-proteins Adenylyl Cyclase Cyclic AMP Protein Kinases Target Proteins Receptors activate many G-proteins, adenylyl cyclase generates many cAMP, protein kinases phophorylate many target proteins 2) A) What is a second messenger and what do they do? B) List five second messengers and an intracellular target for each. a) Second messengers are intracellular signaling molecules that are not directly activated by an extracellular signal. Instead, second messengers are a downstream component of a signaling pathway. b) Ca++ targets Calmodulin cAMP, PKA cGMP, PKG IP3, IP3 receptors Diacylglyerol, PKC 3) Describe the Activation/Inactivation cycles of each monomeric and heterotrimeric G-proteins. Include the actions of G-protein subunits, nucleotides, and other relevant protiends. What major similarities stand out? Heterotrimeric G-proteins: An α-subunit bound to GDP forms an inactive trimer with β- and γ- subunits. When an extracellular signal activates the G-protein coupled receptor (GPCR), the G-protein (αβγ) then binds to the receptor. GDP is replaced with GTP, the α-subunit dissociates from βγ and both act on downstream effectors. GAP eventually cleaves GTP to GDP so that GDP bound α- and βγ can re- associate. Monomeric G-proteins: Ras, an example of a monomeric G-protein, in its inactive form is bound to GDP. When a GPCR become activated by and extracellular signal,
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Ras binds to the receptor and its GDP is replaced with GTP. Ras, now active, dissociates from the receptor to effect downstream proteins. GAP eventually cleaves the GTP, inactivating Ras. Similarities include the use of nucleotide GTP and GDP for G-protein regulation, activation through a GPCR and inactivation through GAP. 4) How is the activation of protein kinases typically regulated? Describe the activation of Protein Kinase C and all relevant domains. Protein Kinases typically consist of catalytic and regulatory subunits. Regulatory
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This note was uploaded on 12/09/2010 for the course BIPN BIPN 140 taught by Professor Spitzer during the Spring '07 term at UCSD.

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Problem Set 6 - Problem Set 6 1 List six steps of signal transduction from ligand to downstream target Which steps amplify the signal Ligand

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