ATPase activity and its temperature compensation of the cyanobacterial clock protein KaiC
ATPase activity and its temperature compensation of the cyanobacterial clock protein KaiC
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DOI：
10.1111/j.1365-2443.2008.01174.x
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发表时间：
2008-04-01
期刊：
影响因子：
2.1
通讯作者：
Ishiura, Masahiro
中科院分区：
文献类型：
--
作者：
Murakami, Reiko;Miyake, Ayumi;Ishiura, Masahiro
KaiA、KaiB和KaiC构成了蓝藻的生物钟机制。KaiC是一种同型六聚体;其亚基包含重复的两半，每一半都有一组ATP酶基序。在这里，使用高度纯化的KaiC制剂的嗜热蓝细菌长形热聚球藻BP-1在大肠杆菌中产生的，我们发现，N-和C-末端结构域的KaiC有非常弱的ATP酶活性。ATP酶活性在野生型KaiC中表现出温度补偿，但在缺少两个磷酸化位点的突变体KaiC（S431 A/T432 A）中没有。我们的结论是KaiC磷酸化参与了ATP酶的温度补偿机制，这可能对蓝藻生物钟的稳定性至关重要，我们假设了以下温度补偿机制：（i）KaiC六聚体亚基的C端磷酸化位点被相邻KaiC亚基的C端结构域磷酸化;（ii）磷酸化抑制C-末端结构域的ATP酶活性;和（iii）磷酸化的KaiC自发去磷酸化，导致ATP酶活性的恢复。
KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria. KaiC is a homohexamer; its subunit contains duplicated halves, each with a set of ATPase motifs. Here, using highly purified KaiC preparations of the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 produced in Escherichia coli, we found that the N- and C-terminal domains of KaiC had extremely weak ATPase activity. ATPase activity showed temperature compensation in wild-type KaiC, but not in KaiC(S431A/T432A), a mutant that lacks two phosphorylation sites. We concluded that KaiC phosphorylation is involved in the ATPase temperature-compensation mechanism-which is probably critical to the stability of the circadian clock in cyanobacteria-and we hypothesized the following temperature-compensation mechanism: (i) The C-terminal phosphorylation sites of a KaiC hexamer subunit are phosphorylated by the C-terminal domain of an adjacent KaiC subunit; (ii) the phosphorylation suppresses the ATPase activity of the C-terminal domain; and (iii) the phosphorylated KaiC spontaneously dephosphorylates, resulting in the recover of ATPase activity.