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Chapter 11 - Prokaryote Gene Regulation.pdf - Regulation of...

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Regulation of GeneExpression in Bacteriaand their VirusesCHAPTER 11
OUTLINE1.)Lac OperonNegative Control2.) Lac OperonPositive Control3.) Arabinose Operon4.) Tryptophan Operon5.) Alternative Sigma Factors
Bacterial MetabolismBacteria arenutritional opportunists.Can obtain nutrients from environment:sugars, amino acids, and nucleotides,Or they can synthesize their own nutrientsNatural selection favors efficiency and selects against the waste of resources and energy.Bacteria will synthesize the enzymes necessary to produce compounds only when there is noother option
Bacterial MetabolismBacteria regulatory systems couple gene expressionto sensory systemsExampleSugar metabolismDifferent types of sugar: lactose, glucose, galactose, and xylose.A different import protein is required to allow each of these sugars to enter the cell.A different set of enzymes is required to process each of the sugars.Gene Regulation allows us to1.Shut down (repress) the transcription of all genes encoding enzymes that are not needed2.Turn on (activate) those genes encoding enzymes that are needed.
Bacterial Gene RegulationTwo criteria for gene regulation of prokaryotes:1.They must be able to recognize environmentalconditions in which they should activate orrepress the transcription of the relevant genes.2.They must be able to turn on or off thetranscription of each specific gene or group ofgenes.
Genetic SwitchesRegulation of transcription depends mainly on two typesofproteinDNA interactions.1.) Determines where transcription beginsPromoter/RNA polymerase.2.) Determines whether transcription takes place.ActivatorsandRepressorsproteins that bind toDNAsegments near the promoterOperons -a segment of DNA that encodes a multigenicmRNA as well as an adjacent common promoter andregulatory region.Operators- binding sites for repressorsPositive Regulation-an activator protein binds to its targetDNA site as a necessary prerequisite for transcription tobegin.Negative Regulation -repressor protein must be preventedfrom binding to its target site as a necessary prerequisite fortranscription to begin.
Genetic SwitchesHow do activators and repressors regulatetranscription?
Genetic SwitchesRegulatory proteins possess twodifferent sites1.)DNA-binding domain2.) allosteric site-acts as a sensor that sets theDNA-binding domain in one of two modes:functional or nonfunctional.allosteric effectorssmall molecules interactwith the allosteric site.

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Term
Fall
Professor
hegde

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