Lecture 7 8. 1 Major Modes of Regulation 8.2 Inhibiting Enzyme Activity 8.3 Modification of Enzymes 8.4 dNA Binding Proteins 8.5 Negative Control of Transcription Repression and Induction 8.6 Positive Control of transcription
Lecture 7 • 8.1 Major Modes of Regulation • 8.2 Inhibiting Enzyme Activity • 8.3 Modification of Enzymes • 8.4 DNA Binding Proteins • 8.5 Negative Control of Transcription: Repression and Induction • 8.6 Positive Control of Transcription
Regulation different conditions require different strategies changes in nutrients available sporulation impractical to make every protein excess proteins may be detrimental allows specific response activities can be regulated at multiple levels
Regulation • different conditions require different strategies – changes in nutrients available – sporulation • impractical to make every protein • excess proteins may be detrimental • allows specific response • activities can be regulated at multiple levels
Different Regulatory Mechanisms Regulate Regulate enzyme synthesis enzyme activity At translation At transcription Substrate Product No product Enzyme a En zyme No enzyme Translation No mRNA Transcription 米 》 Gene A Gene B Gene C Gene D Figure 8.1
Figure 8.1 Different Regulatory Mechanisms
Feedback Inhibition Starting material Enzyme A First intermediate Enzyme B Second intermediate Enzyme C Third intermediate Enzyme D End product Figure 8.2
Figure 8.2 Feedback Inhibition
Allosteric Effector Substrate Allosteric site binding site Allosteric flector Substrate Conformational change in substrate binding site: enzyme reaction inhibited Substrate cannot bind No enzyme Figure 8.3
Figure 8.3 Allosteric Effector
Feedback Inhibition Branched Biosynthetic Pathway Glutamic acid AGS GK Feedback Feedback inhibition I I inhibition Proline Figure 8. 4 Arginine
Figure 8.4 Feedback Inhibition, Branched Biosynthetic Pathway
Feedback Inhibition of a Common Pathway Phosphoenol erythrose 4-phosphate pyruvate (PHE (TRP) DAHP synthetases(1, 2, 3) DAHP Chorismate Figure 8.5 Tyrosine Tryptophan Phenylalanine
Figure 8.5 Feedback Inhibition of a Common Pathway
Enzyme modifications covalent modification changes protein conformation addition of amp adp phosphorylation methylation
Enzyme Modifications • covalent modification changes protein conformation – addition of AMP, ADP – phosphorylation – methylation
Adenylation of Glutamine Synthetase P Glutamine GS GS concentration AMP(1-12) (a 8 0 Figure 8.6 AMP groups added
Figure 8.6 Adenylation of Glutamine Synthetase
Repression of Enzyme Activity S Number of cells Total protein Arginine added Enzymes involved in arginine synthesis Figure 8.10 Time
Figure 8.10 Repression of Enzyme Activity