《微生物学》课程PPT课件讲稿（英文版）Lecture 7

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