Part:BBa_K2637001

KaiA Protein of Circadian Rhythm

KaiA is one of the essential proteins in the circadian rhythm of cyanobacterias. It can regulate the process of KaiC’s phosphorylation and dephosphorylation together with KaiB and other proteins in our system, and then drive the cyanobacterias into subjective dawn or dusk. We have optimized it in yeast.

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Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BglII site found at 832
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]

Biology and Usage

Overview of Cyanobacterias' circadian rhythm

[[Image:zhaohaoqian.png|center|frame|300px|Figure 1. interaction among the proteins ]

Organisms are adapted to the relentless cycles of day and night, because they evolved timekeeping systems called circadian clocks, which regulate biological activities with ~24-hour rhythms. The clock of cyanobacteria is driven by a three-protein oscillator composed of only three protein KaiA, KaiB and KaiC, which together generate a circadian rhythm of KaiC phosphorylation at residues serine 431 and threonine 432 in the CII dimain. KaiA promotes KaiC (auto)phosphorylation during the subjective day, whereas KaiB provides negative feedback to inhibit KaiA and promotes KaiC (auto)dephosphorylation during the subjective night. The 24-h KaiC phosphorylation pattern can be reconstituted in vitro by merely combining the three Kai proteins and ATP, suggesting that the phosphorylation cycle is the fundamental timekeeping mechanism in cyanobacteria. Like KaiA, KaiB is also involved in regulating two antagonistic clock-output proteins--SasA and CikA, which reciprocally control the master regulator of transcription RpaA.