IGEM:Harvard/2006/Brainstorming Papers - Hetmann

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Cyanobacteria Oscillators

  1. Wang J. Recent cyanobacterial Kai protein structures suggest a rotary clock. Structure. 2005 May;13(5):735-41. DOI:10.1016/j.str.2005.02.011 | PubMed ID:15893664 | HubMed [1]
  2. Nakajima M, Imai K, Ito H, Nishiwaki T, Murayama Y, Iwasaki H, Oyama T, and Kondo T. Reconstitution of circadian oscillation of cyanobacterial KaiC phosphorylation in vitro. Science. 2005 Apr 15;308(5720):414-5. DOI:10.1126/science.1108451 | PubMed ID:15831759 | HubMed [2]
  3. Imai K, Nishiwaki T, Kondo T, and Iwasaki H. Circadian rhythms in the synthesis and degradation of a master clock protein KaiC in cyanobacteria. J Biol Chem. 2004 Aug 27;279(35):36534-9. DOI:10.1074/jbc.M405861200 | PubMed ID:15229218 | HubMed [3]
  4. Naef F. Circadian clocks go in vitro: purely post-translational oscillators in cyanobacteria. Mol Syst Biol. 2005;1:2005.0019. DOI:10.1038/msb4100027 | PubMed ID:16729054 | HubMed [4]
All Medline abstracts: PubMed | HubMed

[Full text article of Naef]

[Full text article of Wang J.]

Nakajima et. al

  • cyanobacterium Synechococcus elongatus (PCC 7942)
  • three genes components (kaiA, kaiB, and kaiC)
  • Kai proteins regulate the kaiBC operon
    • Oscillation of KaiC phosphorylation cycle is the pacemaker, molecular timer
    • KaiA enhances KaiC autophosphorylation
    • KaiB attenuates the effect of KaiA
    • Oscillation of KaiC phosphorylation maybe generated by KaiA and KaiB cooperation
  • Nakajima et. al incubated recombinant KaiC protein with KaiA and KaiB at a ratio similar to in vivo to test it in vitro
  • KaiC phosphorylation oscillated robustly without damping
  • KaiC not degraded during the reaction
  • Oscillation of KaiC phosphorylation is autonomous due to cooperation of three Kai proteins
  • The thermal sensitivity in vitro same as in vivo gene expression rhythm
  • They found that KaiC phosphorylation is the molecular timer for the circadian rhythm of Synechococcus
  • KaiC hexamer may have many phosphorylation states with different biochemical characteristics
  • In addition, the reaction rate of KaiC phosphorylation and dephosphorylation are slow reducing the energy needed

[Nakajima et. al article]