regulation of gene and cellular activity
DESCRIPTION
Regulation of gene and cellular activity. Regulating Gene Expression. Cells use different mechanisms to sense and respond to conditions within or outside the cell. Regulatory proteins help a cell sense internal changes and alter its gene expression to match. Figure 10.1A. Figure 10.1B and C. - PowerPoint PPT PresentationTRANSCRIPT
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Regulation of gene and cellular activity
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• Cells use different mechanisms to sense and respond to conditions within or outside the cell.
• Regulatory proteins help a cell sense internal changes and alter its gene expression to match.
Regulating Gene Expression
Figure 10.1A
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Figure 10.1B and C
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Figure 10.3
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• Microbes control gene expression at several levels:
• - Alterations of DNA sequence• - Control of transcription • - Control of mRNA stability• - Translational control• - Posttranslational control
Regulating Gene Expression
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• The lactose utilization lacZYA operon of E. coli was the first gene regulatory system described.
• First, here’s how lactose is transported and metabolized.
The E. coli Lactose Operon
Figure 10.6
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The Organization of the LacZYA OperonFigure 10.5A
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• LacI binds as a tetramer to the operator region.• - It represses the lac operon by preventing open
complex formation by RNA polymerase.
Scenario 1: Absence of Lactose
Figure 10.5B
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• b-galactosidase (LacZ), when at low concentrations, cleaves and rearranges lactose to make the inducer allolactose.
• Allolactose binds to LacI, reducing its affinity to the operator and thus allowing induction of the operon.
Scenario 2: Presence of Lactose
Figure 10.5C
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• Maximum expression of the lac operon requires the presence of cAMP and cAMP receptor protein (CRP).
• - The cAMP-CRP complex binds to the promoter.• - Interacts with RNA pol to increase the rate of
transcription initiation
Activation of the lac Operon by cAMP-CRP
Figure 10.8
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Catabolite Repression• In catabolite repression, an
operon enabling the catabolism of one nutrient is repressed by the presence of a more favorable nutrient (commonly glucose).
The biphasic curve of a culture growing on two carbon sources is often called diauxic growth.
Figure 10.10
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Catabolite Repression
• Glucose transport by the phosphotransferase system causes catabolite repression by inhibiting the LacY permease activity.
• - This is termed inducer exclusion.
Figure 10.11
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• Animation: The lac operon
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The E. coli Lactose Operon
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Figure 10.15
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• Attenuation is a regulatory mechanism in which translation of a leader peptide affects transcription of a downstream structural gene.
Attenuation of the trp Operon
Figure 10.16A
The attenuator region of the trp operon has 2 trp codons and is capable of forming stem-loop structures.
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The Transcriptional Attenuation Mechanism of the trp Operon
Figure 10.16B and C
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Figure 10.18
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Figure 10.24
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Figure 10.26A
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Figure 10.28
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• Quorum sensing refers to the process where bacterial cells work together at high density.
Quorum Sensing
- It was discovered in Vibrio fischeri, a bioluminescent bacterium that colonizes the light organ of the Hawaiian squid.
Figure 10.30ACD
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Figure 10.31
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• Animation: Transcriptional Attenuation
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Transcriptional Attenuation
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• Animation: Chemotaxis: Molecular Events
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Chemotaxis: Molecular Events
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• Animation: Quorum Sensing
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Quorum Sensing