13_lecture - Chapter 13 Regulation of Cellular Processes 1...

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Unformatted text preview: Chapter 13 Regulation of Cellular Processes 1 regulation of gene expression transcription initiation transcription elongation translation alter activity of enzymes and proteins posttranslational three domains of life differ in genome structure and regulatory mechanisms used 2 Two Approaches to Regulation Steps Leading from the Information Coded in DNA to a Functional Protein Bacteria Archaea 3 4 Figure 13.1 replacement of degraded enzymes constitutive genes are housekeeping genes that are expressed continuously by the cell inducible genes are genes that code for inducible enzymes needed only in certain environments such as -Galactosidase 5 Regulation of Transcription Initiation inducible enzyme functions in a catabolic pathway inducible enzymes are present only when their substrate (inducer - effector molecule) is available -galactosidase reaction catalyzed is lactose hydrolysis into galactose and glucose 6 Inducible Genes -Galactosidase Enzyme 7 Figure 13.2 enzymes that function in biosynthetic pathways are products of repressible genes generally these enzymes are always present unless the end product in the biosynthetic pathway is available 8 Repressible Genes induction and repression occur because of the activity of regulatory proteins and DNA binding domains these proteins either inhibit transcription (negative control) or promote transcription (positive control) 9 Control of Transcription Initiation by Regulatory Proteins binding of regulatory protein (repressor) at DNA regulatory site (operator) inhibits initiation of transcription mRNA expression is reduced repressor proteins exist in active and inactive forms inducers (substrates) and corepressors (enzymatic products) alter activity of repressor by binding 10 Negative Transcriptional Control 11 Figure 13.3(a) and (b) binding of a regulatory protein (activator protein) at a regulatory region on DNA (activator binding sites) promotes transcription initiation mRNA synthesis is increased activation inactive protein is activated by inducer (activator protein) active protein is inactivated by inhibitor 12 Positive Control 13 Figure 13.3(c) and (d) enzymes of a catabolite pathway are only needed (increased mRNA synthesis) when the preferred substrate is available enzymes not synthesized when substrate absent efficient use of energy and materials 14 Decision Process in Gene Expression 15 Figure 13.4 promoter and operator or activator-binding sites, along with functionally related structural genes, are grouped together in the DNA...
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13_lecture - Chapter 13 Regulation of Cellular Processes 1...

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