IGEM:Harvard/2006/Brainstorming Papers - Hetmann

Cyanobacteria Oscillators

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[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]