Crystal structure of the C-terminal clock-oscillator domain of the cyanobacterial KaiA protein
Crystal structure of the C-terminal clock-oscillator domain of the cyanobacterial KaiA protein
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DOI：
10.1038/nsmb781
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发表时间：
2004-07-01
影响因子：
16.8
通讯作者：
Ishiura, M
中科院分区：
文献类型：
--
作者：
Uzumaki, T;Fujita, M;Ishiura, M
KaiA、KaiB和KaiC构成蓝藻的生物钟机制，KaiA激活kaiBC的表达，而KaiC抑制kaiBC的表达。我们发现KaiA由三个功能域组成，n端振幅放大器域、中心周期调节器域和c端时钟振荡器域。c端结构域负责二聚体的形成，与KaiC结合，增强KaiC磷酸化并产生昼夜节律振荡。对嗜热蓝藻热共生球菌（Thermosynechococcus elongatus BP-1）的KaiA c端时钟振荡器域1.8埃分辨率的x射线晶体结构进行了分析，结果表明，位于KaiA二聚体凹陷中心的残基His270对KaiA的功能至关重要。KaiA与KaiC的结合可能是通过凹面发生的。在结构的基础上，我们预测了影响昼夜振荡的残基的结构作用。
KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria, and KaiA activates kaiBC expression whereas KaiC represses it. Here we show that KaiA is composed of three functional domains, the N-terminal amplitude-amplifier domain, the central period-adjuster domain and the C-terminal clock-oscillator domain. The C-terminal domain is responsible for dimer formation, binding to KaiC, enhancing KaiC phosphorylation and generating the circadian oscillations. The X-ray crystal structure at a resolution of 1.8 Angstrom of the C-terminal clock-oscillator domain of KaiA from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 shows that residue His270, located at the center of a KaiA dimer concavity, is essential to KaiA function. KaiA binding to KaiC probably occurs via the concave surface. On the basis of the structure, we predict the structural roles of the residues that affect circadian oscillations.