Williams Stanly B, Vakonakis Ioannis, Golden Susan S, LiWang Andy C
Department of Biology, Texas A&M University, College Station 77843, USA.
Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15357-62. doi: 10.1073/pnas.232517099. Epub 2002 Nov 15.
In the cyanobacterium Synechococcus elongatus (PCC 7942) the proteins KaiA, KaiB, and KaiC are required for circadian clock function. We deduced a circadian clock function for KaiA from a combination of biochemical and structural data. Both KaiA and its isolated carboxyl-terminal domain (KaiA180C) stimulated KaiC autophosphorylation and facilitated attenuation of KaiC autophosphorylation by KaiB. An amino-terminal domain (KaiA135N) had no function in the autophosphorylation assay. NMR structure determination showed that KaiA135N is a pseudo-receiver domain. We propose that this pseudo-receiver is a timing input-device that regulates KaiA stimulation of KaiC autophosphorylation, which in turn is essential for circadian timekeeping.
在蓝藻聚球藻（PCC 7942）中，蛋白质KaiA、KaiB和KaiC是昼夜节律钟功能所必需的。我们通过生化和结构数据的结合推断出KaiA的昼夜节律钟功能。KaiA及其分离的羧基末端结构域（KaiA180C）均刺激KaiC自磷酸化，并促进KaiB对KaiC自磷酸化的减弱。氨基末端结构域（KaiA135N）在自磷酸化测定中无功能。核磁共振结构测定表明，KaiA135N是一个假受体结构域。我们提出，这个假受体是一个定时输入装置，可调节KaiA对KaiC自磷酸化的刺激，而这反过来对于昼夜计时至关重要。
