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Lecture 8

Lecture 8. 8.8 Attenuation 8.9 Other Global Control Networks 8.10 Signal Transduction and Two-Component Regulatory Systems 8.11 Regulation of Chemotaxis. RNA and termination. RNA: single stranded nucleic acid can form secondary structures Rho-dependent termination: protein signal

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Lecture 8

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  1. Lecture 8 • 8.8 Attenuation • 8.9 Other Global Control Networks • 8.10 Signal Transduction and Two-Component Regulatory Systems • 8.11 Regulation of Chemotaxis

  2. RNA and termination • RNA: single stranded nucleic acid • can form secondary structures • Rho-dependent termination: protein signal • Rho-independent signal: hairpin or stem-loop RNA structure, followed by several uracils

  3. Tryptophan Operon Figure 8.20

  4. Tryptophan Operon: mRNA 1 2 3 4 trpE  • regions 1, 2: synthesis of leader peptide • regions 2, 3: form stem-loop structure • regions 3, 4: form stem-loop structure

  5. Attenuation Figure 8.21

  6. Figure 8.22 Bioluminescent Vibrio fischeri

  7. Vibrio bioluminescence • Vibrio fischeri inhabits the open sea (in small densities), as well as in squid light organs (in high densities) • Luminescence occurs only at high cell concentrations

  8. Quorum Sensing • Regulation of genes expression in response to population density • Acylated homoserine lactone (AHL) molecules might be produced and excreted by all cells in a given population • Higher population density results in greater concentration of AHL • AHL molecules activate a specific transcriptional activator protein, resulting in specific transcription induction

  9. Quorum-sensing model from University of Nottingham Quorum Sensing Research Group (Paul Williams)

  10. Two-component regulatory system Figure 8.23

  11. Chemotaxis Figure 8.24

  12. Chemotaxis in Review • no attractant: CheACheA-P, CheY-P • tumble • attractant: MCP blocks CheA-P • CheZ: CheY-PCheY • run • over time: CheR methylates, desensitizes MCP • new baseline: as if no attractant present • CheACheA-P, CheY • tumble • CheB-P demethylates, re-sensitizes MCP

  13. Taxis Receptors • multiple MCPs sense different substrates • other, similar systems respond to different conditions (light, oxygen, etc.) • taxic responses studied by mutational analyses

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