Day_6_-_Global_Networks_and_Quorum_Sensi

Day_6_-_Global_Networks_and_Quorum_Sensi - Global...

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Global Regulatory Networks Quorum Sensing and Inter-kingdom Signaling Chapter 13
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Global Control Networks A. Global control systems allow organisms to respond effectively to signals in the environment. B. Global control systems are essentially stimulons that are activated by environmental signals, and often include many regulons . Catabolite repression is a global control system (cAMP-CRP). C. The regulatory elements of global control systems can be: 1. Activator or repressor proteins similar to CAP and TRAP. 2. Sensor/response regulator phosphorelay proteins. 3. Complements of Riboswitches (least well characterized). 3. Sigma factors.
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Some E. coli global control systems that use signaling through repressor or activator proteins are: System Signal Regulatory Protein No. of genes Aerobic respiration O 2 ArcA repressor 50+ Anaerobic respiration Lack of O 2 FNR activator 70+ Catabolite repression [cAMP] CAP activator 300+ Oxidative stress Oxidizing agent OxyR activator 30+ SOS response Damaged DNA LexA repressor 20+
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PTS-mediated glucose transport PTS = PEP-dependent phosphotransferase system HPr -His~P PE~P Pyruvate EI ATP Glucose Glucose-6-P out in EIIC EIIB P P EIIA cAMP ATP ATP AC CAP CAP cAMP cAMP araoperon lacoperon maloperon etc. Catabolite-Repression in E. coli POSITIVE REGULATION Lack of glucose stimulates transcription of target operons A C T I V A T I O N
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No glucose Glucose Glucose-6-P PTS-mediated glucose transport HPr - His ~P PE~P Pyruvate EI out in EIIC EIIB P P EIIA araoperon sacoperon galoperon Catabolite-Repression in B. subtilis NEGATIVE REGULATION Available glucose inhibits transcription of target operons ATP Fructose-1,6-P ADP [high] HPr Negative or positive operon-specific regulation ATP ADP HPrK HPr (HPr kinase) ~ 100 genes HPr CcpA (Catabolite control protein) B. subtilis does not use lactose, but can use saccharose (sucrose) cre REPRESSION
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Signal Transduction and Two Component Regulatory Systems So far, we have dealt with regulatory systems that use small molecules that enter the cell and act as effectors by combining with proteins that directly activate or inactivate transcription. A. In Prokaryote and Eukaryotes, many signals are first detected by a sensor and then transmitted in a changed form to the rest of the regulatory machinery by a process called signal transduction . B. In general, signal transduction involves two components: 1. A sensor protein (sensor kinase) which phosphorylates itself after binding a cognate signal molecule ( autophosphorylation ; usually at a histidine ) . 2. A response-regulator protein to which the sensor protein transfers the phosphate group, often to an aspartic acid . C. The phosphorylated response-regulator protein may bind directly to the DNA and regulate transcription or convert other proteins to be the final response regulators ( phosphorelay ).
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A Simple Two Component Regulatory System Transcription activated or blocked Sensor kinase Response regulator Phosphatases can act as “response inhibitors” ATP ADP GTP GDP or
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This note was uploaded on 09/14/2010 for the course MMG 431 taught by Professor Bertrand during the Fall '08 term at Michigan State University.

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Day_6_-_Global_Networks_and_Quorum_Sensi - Global...

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