reactions and gene expression [7,8]. 反应与基因的表现形式(文献7,8)Despite such fluctuations in the cellular milieu, the S. elongatus clock oscillates with high precision and minimal damping for weeks in constant conditions [8,9].在恒定条件下,尽管有细胞媒介的变异,S型的细长生物钟仍然能够在高度的准确性和最小的衰减下,周期性地工作几个星期。Somehow, the clock is sufficiently robust to avoid a loss of synchrony and the resulting spiral into a steady state.生物钟足以能够避免同步性的丧失,并能够螺旋式地进入稳定状态,这一点,目前还不清楚其原因。Circadian oscillators evolved long ago, but our understanding of the molecular mechanisms underlying circadian clocks remains murky. 生物节律已经研究了很久,但是我们对生物钟的分子层次的理解仍然是模糊不清的。These mechanisms have been investigated primarily in cyanobacteria, fungi, flies, plants, and mammals. 这方面的最初研究是通过藻青菌、真菌、飞虫、植物和哺乳动物进行的。The prevailing models for the internal timepieces of all but the first of those organisms involve a negative transcriptional feedback loop in which so-called clock genes encode proteins that repress theirown transcription. 对于所有生物(不是第一生物)的内部生物钟的主流性的模型包括了阴性的一个反馈式的转录环,此环被称为时钟基因,它给予蛋白质基因密码,抑制其自身转录。These negative feedback loops typically are intertwined with other feedback loops and are overlaid with post-translational regulation affecting protein stability, activity, and localization [1].通常这种阴性的反馈环与转录后的机制互相缠绕、互相重叠,从而影响到蛋白质的稳定性、活跃性和定位性。(文献1)Disentangling the mechanisms and rigorously testing models of these oscillators have been hampered by the complexity of both the osillators themselves and the cellular environment in which they are embedded.探清生物钟的机制和对其进行严格的测试工作,由于生物钟以及它们赖以生存的细胞环境的复杂性而受到阻碍。An opportunity to break through such complexity recently emerged from investigations of the circadian clock of S. elongatus, whose core oscillator consists of just three proteins: KaiA, KaiB,and KaiC. 打破这种复杂性的机会,最近终于浮现,通过对S型细长的生物钟的研究发现,这种周期性的生物节律由三种蛋白质所形成:KaiA, KaiB,和 KaiC。Although the oscillator originally was thought to be a transcriptional feedback oscillator analogous to those found inhigher organisms [10], Kondo and colleagues showed in 2005 that the clock of S. elongatus requires neither transcription nor translation–oscillations in KaiC phosphorylation state persist in the absence of transcriptional feedback and protein synthesis [4].虽然原始的生物钟是模拟高等生物的转录反馈生物节律,但是Kondo和他的同事们在2005年证实S型细长生物钟既不需要转录,也不需要转译---在缺乏转录反馈和蛋白质合成的情况下,在KaiC磷酸化的状态,生物节律仍然持续。(文献4)Remarkably, the Kai proteins themselves constitute a circadian clock: temperature-ompensated circadian oscillations in KaiC phosphorylation can be reconstituted in vitro by combining the three Kai proteins and adenosine triphosphate (ATP) [11]. 显然地,KaiC 蛋白质自身构成了一个生物钟:在磷酸化状态下的温度补偿式的生物钟,结合三种 Kai 蛋白质与三磷酸腺苷,在玻璃试管内可以重构生物钟。This three-protein, test-tube oscillator displays all three cardinal properties of a circadian clock: free-run, temperature compensation,and entrainment [11–13]. 这种三蛋白质试管内的生物钟显示了所有生物钟的三种基本特性:自由进行、温度补偿和调节。(文献11-13)Oscillations of KaiC phosphorylation free-run for at least 10 days in vitro [14], and the period of oscillation is temperature-compensated [11,13]. 这种 KaiC 磷酸化状态下自由进行的生物钟在试管中可以至少持续10天(文献14),生物钟的周期是温度补偿式的(文献14)。The phase of the in vitro clock is phase-shifted by, and entrainable to, temperature shifts [12,13], although it is not entrainable by light, presumably because cellular components required for this property are absent 2. 这种在试管中的生物钟会有相移,如温度引起的相移,不过可以调节,虽然现在不可以用光来调节,因为缺乏所需要的细胞成分。Biochemistry of the Kai oscillator The ability to reconstitute the oscillator in vitro and to mix and match its four components (KaiA, KaiB, KaiC, and ATP) in arbitrary combinations has permitted detailed, quantitative biochemical characterization of the Kai proteins. Kai 生物钟的生物化学。在试管中以任意的组合方式,与四种成分(KaiA, KaiB, KaiC, 和三磷酸腺苷)的混合与配对,用以重建生物钟的能力已经细制的进入了蛋白质的生物化学方面的定量分析了。Structures of all three proteins (or their homologs in related organisms) have been solved by 所有三种蛋白质的结构,以及在有关的生物体的同系物中,已经由....解决了。