Ditty J L, Williams S B, Golden S S
Department of Biology, University of St. Thomas, St. Paul, Minnesota 55105, USA.
Annu Rev Genet. 2003;37:513-43. doi: 10.1146/annurev.genet.37.110801.142716.
Cyanobacteria such as Synechococcus elongatus PCC 7942 exhibit 24-h rhythms of gene expression that are controlled by an endogenous circadian clock that is mechanistically distinct from those described for diverse eukaryotes. Genetic and biochemical experiments over the past decade have identified key components of the circadian oscillator, input pathways that synchronize the clock with the daily environment, and output pathways that relay temporal information to downstream genes. The mechanism of the cyanobacterial circadian clock that is emerging is based principally on the assembly and disassembly of a large complex at whose heart are the proteins KaiA, KaiB, and KaiC. Signal transduction pathways that feed into and out of the clock employ protein domains that are similar to those in two-component regulatory systems of bacteria.
诸如聚球藻7942（Synechococcus elongatus PCC 7942）之类的蓝细菌表现出基因表达的24小时节律，该节律由内源性生物钟控制，其机制与多种真核生物中描述的生物钟不同。在过去十年中，遗传和生化实验已经确定了昼夜节律振荡器的关键组件、使生物钟与日常环境同步的输入途径以及将时间信息传递给下游基因的输出途径。正在形成的蓝细菌生物钟机制主要基于一个大型复合体的组装和拆卸，其核心是KaiA、KaiB和KaiC蛋白。进出生物钟的信号转导途径使用的蛋白质结构域类似于细菌双组分调节系统中的结构域。
