Cooperative KaiA-KaiB-KaiC interactions affect KaiB/SasA competition in the circadian clock of cyanobacteria.
Cooperative KaiA-KaiB-KaiC interactions affect KaiB/SasA competition in the circadian clock of cyanobacteria.
复制标题
DOI：
10.1016/j.jmb.2013.09.040
复制
发表时间：
2014-01-23
影响因子：
5.6
通讯作者：
Liwang A
中科院分区：
文献类型：
--
作者：
Tseng R;Chang YG;Bravo I;Latham R;Chaudhary A;Kuo NW;Liwang A
蓝藻的昼夜节律振荡器仅由KaiA、KaiB和KaiC三种蛋白质组成。它们共同产生KaiC磷酸化的自主~24小时生化节律。KaiA通过与KaiC的所谓A环结合来刺激KaiC磷酸化，而KaiB将KaiA隔离在KaiABC复合物中远离A环，从而诱导KaiC去磷酸化。从KaiC磷酸化到去磷酸化的转换是由KaiB-KaiC复合物的形成引发的，其发生在KaiC的S431残基的磷酸化之后。我们在这里表明，KaiB-KaiC复合物的形成是由KaiA促进的，这表明在脱磷酸化复合物的起始中存在协同性。在KaiA-KaiB相互作用中，KaiB的一个单体亚基可能与KaiA二聚体的一面结合，而另一面未被占据。我们还表明，KaiC的A-回路存在于KaiA-可访问的暴露和KaiA-不可访问的埋藏位置之间的动态平衡。KaiC的S431残基处的磷酸化使A环向掩埋位置移动，从而减弱KaiA-KaiC相互作用，这预计是促进KaiABC复合物形成的额外机制。我们还表明，KaiB和时钟输出蛋白SasA竞争重叠的结合位点，其中包括KaiC的CI环上的B环。KaiA强烈地将竞争转移到KaiB的有利位置。因此，除了刺激KaiC磷酸化之外，KaiA可能在KaiC从磷酸化到去磷酸化的转换中发挥作用，以及调节时钟输出。
The circadian oscillator of cyanobacteria is composed of only three proteins, KaiA, KaiB, and KaiC. Together, they generate an autonomous ~24-h biochemical rhythm of phosphorylation of KaiC. KaiA stimulates KaiC phosphorylation by binding to the so-called A-loops of KaiC, whereas KaiB sequesters KaiA in a KaiABC complex far away from the A-loops, thereby inducing KaiC dephosphorylation. The switch from KaiC phosphorylation to dephosphorylation is initiated by the formation of the KaiB–KaiC complex, which occurs upon phosphorylation of the S431 residues of KaiC. We show here that formation of the KaiB–KaiC complex is promoted by KaiA, suggesting cooperativity in the initiation of the dephosphorylation complex. In the KaiA–KaiB interaction, one monomeric subunit of KaiB likely binds to one face of a KaiA dimer, leaving the other face unoccupied. We also show that the A-loops of KaiC exist in a dynamic equilibrium between KaiA-accessible exposed and KaiA–inaccessible buried positions. Phosphorylation at the S431 residues of KaiC shift the A-loops toward the buried position, thereby weakening the KaiA–KaiC interaction, which is expected to be an additional mechanism promoting formation of the KaiABC complex. We also show that KaiB and the clock-output protein SasA compete for overlapping binding sites, which include the B-loops on the CI ring of KaiC. KaiA strongly shifts the competition in KaiB’s favor. Thus, in addition to stimulating KaiC phosphorylation, it is likely that KaiA plays roles in switching KaiC from phosphorylation to dephosphorylation, as well as regulating clock output.
登录
查看更多内容
DOI：
10.1073/pnas.1104221108
发表时间：
2011-08-30
影响因子：
11.1
作者：
Chang, Yong-Gang;Kuo, Nai-Wei;LiWang, Andy
通讯作者：
LiWang, Andy
影响因子：
8
作者：
Gao, Tiyu;Zhang, Xiaofan;LiWang, Andy
通讯作者：
LiWang, Andy
影响因子：
4.8
作者：
Hitomi, K;Oyama, T;Getzoff, ED
通讯作者：
Getzoff, ED
影响因子：
16
作者：
Kageyama, Hakuto;Nishiwaki, Taeko;Kondo, Takao
通讯作者：
Kondo, Takao
DOI：
10.1073/pnas.222467299
发表时间：
2002-11-26
影响因子：
11.1
作者：
Iwasaki, H;Nishiwaki, T;Kondo, T
通讯作者：
Kondo, T