02-prok-transc_1b-03

02-prok-transc_1b-03 - Transcription and its control in...

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Transcription and its control in prokaryotes 1. The DNA substrate A. Packaging and availability of the DNA B. Number and arrangement of the genes. C. Transcription control sequences. 1. Promoters 2. Sites for activators and repressors. 3. Sites for the regulation of DNA topology. 4. Sites for the termination of transcription. 2. The General Transcription apparatus. A. RNA Polymerase core enzyme. B. RNA Polymerase holoenzymes. C. NusA, GreA, GreB 3. The process of transcription initiation. A. Identifiable kinetic intermediates B. Biochemical characterization of the process. 4. Transcription elongation. A. Pausing, Sliding,Termination, and Arrest. B. Role of the RNA-DNA hybrid. 5. Transcription termination. A. Rho factor. B. Attenuation. C. Other mechanisms. 6. Examples of mechanisms of activation and repression of transcription initiation. A. The lac operon B. Regulation of nitrogen assimilation ( ntr ) genes.
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Interdomain transfer Sliding and hopping How do DNA-binding proteins find their targets?
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Bacterial RNA Pol belongs to a family called “multisubunit RNAP family” Bacterial Yeast
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E. coli RNA polymerase composed of 5 subunits: Subunits: β , β , α (2), ϖ , and σ Core enzyme: β , β , α (2), ϖ Holoenzyme : β , β , ϖ , α (2) and σ The σ subunits give specificity for site of initiation- promoter
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Subunit structure of bacterial RNA polymerase β NTD CTD β α NTD CTD σ DNA Holoenzyme- β βα 2 σ . Functions in initiation. Core enzyme- β βα 2 . Functions in elongation. 160 kDa 150 kDa 40 kDa
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MW= 151,000 MW=155,000 The β and β ’ subunits form the active site The two large subunits are fused in some bacteria. A synthetic fusion of the two E. coli subunits functions in vivo .
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β ’F:bridging helix β G: flap β ’ C: rudder β ’G:loop Highly-conserved parts of RNA Polymerase form the core of the enzyme
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Binding of σ to promoter sequence required to position polymerase The σ factor participates in melting the DNA
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02-prok-transc_1b-03 - Transcription and its control in...

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