lecture_19v32

lecture_19v32 - Lecture 18 Review When(p)ppGpp increases...

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Unformatted text preview: Lecture 18 Review When [(p)ppGpp] increases; rrn transcription decreases Cell wall biosynthesis stops Initiation of replication stops transcription of protein synthesis genes goes down And amino acid biosynthetic genes go up, amino acid transporters go up proteolysis goes up The Stringent Response Translating ribosome RelA Non ‐ translating ribosome or stalled ribosome RelA + Stalled Ribosome Inhibits rrn , t rna, gene involved in replication, cell wall biosyn. Transcription Activates, aa biosynthetic genes, aa transporters, etc. GDP + (P)P i SpoT soluble pppGpp + AMP ppGpp + PP i + P i GTP + ATP (p)ppGpp Activated RelA The system is self correcting! Once translation rates equilibrate with the new concentration of the limiting amino acid, a new steady state is established, What about growth rate control [(p)ppGpp] is inversely proportional to the growth rate μ Relative [ppGpp] 1 2 Decrease Growth Rate: Shift from glucose to acetate Τ ime ln cell # Shift 1. Immediate cessation of growth for some amount of time: rrn, and rprotein synthesis rates stop, like a Lag. 2. When growth resumes it does so at a different rate. Τ ime ln cell # Shift Increase Growth Rate: Shift from acetate to glucose Immediate increase in growth. Immediate increase in r RNA , and rProtein synthesis. Cells want to grow as fast as possible and are “primed” to grow faster. So what is the controversy? Mutant studies have shown that the two processes, growth rate control and stringent control can be decoupled. Mutants have been found that display stringent control but not growth rate control and visa versa. Lecture 19: Coordination and Regulation Reading : Chapter 10.2 Chapter 18.1 ‐ 18.3 Chapter 16.3.4 Chapter 19.3, 19.4 Chapter 12, 228 ‐ 247 Modes of Control: Proteins • Two ways to control proteins: Activity and Level Potential problems with regulation via proteins: Expensive!!! It can be slow, with respect to the generation time. average T 1/2 for Proteins: hours • Activity: • Allosteric interactions • metabolic control ATP, AMP etc. protein ‐ protein control • covalent modification • Phosphorylation • Acetylation • methylation • Uridylation • Level: – Increase protein level, make more of it. – Degradation, get rid of it. • stability of protein effects level and activity. Stabilize the protein increase the level of protein, and therefore activity. Indirect effect on activity. Modes of Control: RNA • General Transcription and Regulation: • Ways of controlling it: Level • Ways of controlling level: Many Transcription 101 • Basic process: 3 stages, Initiation ‐ elongation and termination. Regulation of transcription can occur at any of these three points!...
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This note was uploaded on 12/02/2009 for the course MIC 140 taught by Professor Meeks,singer during the Spring '09 term at UC Davis.

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lecture_19v32 - Lecture 18 Review When(p)ppGpp increases...

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