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Chapter 3 / 第 3 章

Chapter 3 / 第 3 章. 第 3 章 原核生物转录： 机理与调控 3.1 为什么使用 RNA 作为中间物？ 3.2 转录机理 3.3 原核生物基因 表达调控 3.4 实验研究. Chapter 3 Transcription in Prokaryotes: Mechanism and Regulation 3.1 Why Use an RNA Intermediate? 3.2 Mechanism of Transcription 3.3 Regulation of Gene Expression

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Chapter 3 / 第 3 章

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  1. Chapter 3 / 第3章 第3章 原核生物转录： 机理与调控 3.1 为什么使用RNA 作为中间物？ 3.2 转录机理 3.3 原核生物基因 表达调控 3.4 实验研究 Chapter 3 Transcription in Prokaryotes: Mechanism and Regulation 3.1 Why Use an RNA Intermediate? 3.2 Mechanism of Transcription 3.3 Regulation of Gene Expression in Prokaryotes 3.4 Experiments

  2. 3.1 Why Use an RNA intermediate?3.1 为什么使用RNA作为中间物？

  3. Chromosomes are large and complex DNA Protein Low efficiency ! Ribosome

  4. DNA must be stable

  5. One mRNA many proteins

  6. More opportunities for regulation Chapter 3 Chapter 4

  7. 3.2 Mechanism of Transcription3.2 转录机理

  8. 3.2.1 Promoters / 启动子

  9. −10 box and −35 box CCAGGCTTTACACTT - - -CGTATGTTGTGTGGAATT CTTTTTGATGCAATT - - -ACTATAATAGACAGGGTA GGCGGTGTTGACATA - - -GTGATACTGAGCACATCA -35 box -10 box +1

  10. Consensus sequence / 共有序列 Consensus sequence: a generalized sequence from which most actual sequences differ very little or not at all. （共有序列：一种普遍的序列，大多数实际的序列与它相差很小或完全相同。） Consensus sequences TATAAT TTGACA CCAGGCTTTACACTT - - -CGTATGTTGTGTGGAATT CTTTTTGATGCAATT - - -ACTATAATAGACAGGGTA GGCGGTGTTGACATA - - -GTGATACTGAGCACATCA -35 box -10 box +1

  11. 3.2.2 RNA Polymerase / RNA聚合酶

  12. Core enzyme vs. Holoenzyme Core enzyme starts transcription at random Holoenzyme starts transcription at promoters

  13. Catalytic area of RNA polymerase

  14. 3.2.3 Transcription Mechanism3.2.3 转录机理 • Initiation / 起始 • Elongation / 延伸 • Termination / 终止

  15. 1. Initiation / 起始 Step 1 Step 2

  16. Initiation / 起始 Step 3 Step 4

  17. 2. Elongation / 延伸 Transcription bubble

  18. The polymerization reaction聚合反应 RNA synthesis: 5’ → 3’

  19. Proofreading / 校正 U C Remove U Add C

  20. 3. Termination / 终止 Intrinsic termination 内在型终止 ρ-dependent termination ρ依赖型终止

  21. Intrinsic termination / 内在型终止

  22. Base pair / 碱基对

  23. ρ-dependent termination / ρ依赖型终止

  24. Rho proteins X-Ray Crystal Structure Of Rho protein [MMDB ID:24381]

  25. 3.3 Regulation of gene expression in prokaryotes3.3 原核生物基因表达调控 3.3.1 Coordinate Regulation 3.3.2 The Lac Operon 3.3.3 The Trp Operon 3.3.4 Ara & Gal Operons 3.3.1 协同调控 3.3.2 乳糖操纵子 3.3.3 色氨酸操纵子 3.3.4 阿拉伯糖与 半乳糖操纵子

  26. Regulation of gene expression基因表达调控 Condition A

  27. Regulation of gene expression基因表达调控 Condition B

  28. 3.3.1 Coordinate Regulation协同调控 Operator 操纵基因

  29. Polycistronic mRNA多顺反子mRNA Polycistronic mRNA Translation Protein 1 Protein 3 Protein 2

  30. 3.3.2 The lac Operon / 乳糖操纵子 The lac operon

  31. 1. The Conditions of lactose Metabolism1.乳糖代谢的条件 乳糖 葡萄糖 半乳糖 E. coli: “This is my favorite!”

  32. How to use lactose / 如何利用乳糖 E. coli: “I need lactose permease, β-galactosidase, and transacetylase.”

  33. When to use lactose / 何时利用乳糖 Glucose + Lactose + Glucose –Lactose + E. coli:“I will use lactose only when there is no glucose and there is lactose.” Glucose – Lactose –

  34. Regulated Expression of Lactose Metabolizing Genes乳糖代谢基因表达调控 1. Negative Regulation – the lac Repressor 负调控──lac阻遏蛋白 2. Positive Regulation – CAP 正调控──CAP

  35. 2. Negative Regulation – the lac Repressor负调控──lac阻遏蛋白

  36. Negative Regulation – the lac Repressor负调控──lac阻遏蛋白

  37. 3. Positive Regulation – CAP正调控──CAP

  38. CAP-cAMP complex CAP CAP cAMP cAMP DNA

  39. Adenylyl Cyclase (AC) O—CH2 A O O P——O OH O Glucose inhibits the activity of AC. ATP AC cAMP

  40. CAP – “The accelerator” lac repressor – “The brake” Brake 刹车 Accelerator 加速器

  41. 3.3.3 The Trp Operon / 色氨酸操纵子 COO – +H3N H C CH2 C COO – CH +H3N H C N H CH CH3 CH N H Tryptophan OH OH

  42. 1. Negative Regulation – High Trp level High tryptophan level: No transcription

  43. Negative Regulation – low Trp level Low tryptophan level: Transcription occurs

  44. lac repressor vs.trp repressor (b) High tryptophan : transcription is repressed. RNA polymerase cannot bind to the promoter Operator Promoter Leader - attenuator trpE trpD Low lactose level Aporepressor dimer Repressor dimer High tryptophan level Tryptophan

  45. Lactose – the inducer Tryptophan – the co-repressor (b) High tryptophan : transcription is repressed. RNA polymerase cannot bind to the promoter Operator Promoter Leader - attenuator trpE trpD Aporepressor dimer Inducer 诱导物 Repressor dimer Co-repressor 辅阻遏物 Tryptophan

  46. The Trp Operon: No positive regulation

  47. 2. Attenuation / 衰减作用 Attenuator: “STOP!” Not all transcription is repressed.

  48. The leader-attenuator region前导子-衰减子区域

  49. The leader-attenuator RNA

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