Day_5_-_Gene_Regulation

Day_5_-_Gene_Regulation - or Control of Cell Metabolism...

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Unformatted text preview: or Control of Cell Metabolism Chapters 12, 13 and parts of Chapter 14 Regulation of Gene Expression 1. Feedback control of enzyme activity: quick response regulation of metabolic activity. 2. Slower systems controlling gene expression: a. inhibition or activation of gene transcription by DNA- binding proteins (positive or negative control). b. inhibition of mRNA translation by proteins or RNAs. c. control of transcription termination by mRNA translation (attenuation). d. control of transcription or translation by the conformation of RNA "leader" sequences riboswitch regulation. 3. Unicellular organisms respond to environmental conditions by regulating the expression of many genes simultaneously (regulons and stimulons). 4 . Unicellular organisms have intraspecies, interspecies and interkingdom communication systems based on the release and sensing of small signal molecules. General Outline of Topics Covered in this Part MMG 431 Regulation of Metabolism In general, all cells use two major mechanisms to adapt their metabolism to the prevailing conditions of their environment: A. Control of the activity of preexisting enzymes a rapid response mechanism also known as feedback inhibition or activation . B. Regulation of the amount of enzymes slow response mechanisms that operate at two levels: 1. Regulation of gene transcription (on, off, and anything in between off and on). 2. Regulation of mRNA translation a type of feedback by proteins and RNAs that lack enzyme activity. The expression of some genes does not appear to be regulated at all: constitutive gene expression . Levels of Regulation of Metabolic Activity Constitutive (unregulated) Feedback Regulation of translation Regulation of transcription IMPORTANT ost catabolic and anabolic processes are controlled by a combination of the three modes of regulation. In this section of the class, only a few examples of well-characterized model systems are presented to acquaint students with the mechanisms involved in the regulation of bacterial gene expression and the control of metabolic processes. Additional gene expression control systems involving two-component regulatory systems, the production of unique RNA polymerases and antitermination will be introduced in the sections dealing with conjugation, transformation and bacteriophage genetics. The end-product of a metabolic pathway acts as an allosteric inhibitor on the enzyme that catalyzes the first reaction in the pathway. The activity of enzyme A is inversely proportional to the concentration of the end product. Feedback Inhibition of Enzyme Activity echanism of Enzyme Inhibition by an Allosteric Effector Most allosteric enzymes consist of multiple interacting subunits, each having a catalytic and an allosteric site....
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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_5_-_Gene_Regulation - or Control of Cell Metabolism...

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