CAJ | 학술논문

生物钟现象是一种普遍存在于生物界细胞的内源节律性保持机制。生物钟机制的存在可以使生物体的代谢行为产生并维持以24 h为周期的昼夜节律，从而更好地适应于地球自转所产生的环境条件昼夜间节律性变化。蓝藻是目前生物钟分子机制研究中的模式生物，其依赖于k ai基因家族成员的核心生物钟调控模式已经被众多研究者详细阐明。蓝藻生物钟的核心振荡器是由蓝藻k aiA/B/C的编码产物来调控的，Kai蛋白的表达模式具有节律性。KaiC蛋白磷酸化状态的节律性循环及输入、输出途径相关组成蛋白的翻译后修饰状态节律性循环共同组成其反馈回路，负责维持生物钟节律性振荡的持续进行并与环境周期保持同步。传统的蓝藻生物钟分子机制模型认为，节律性表达基因翻译产物的转录/翻译负反馈抑制环是生物节律性维持和输出的关键。遗憾的是，在其它物种生物钟分子机制研究中未发现由kai基因家族成员同源基因组成的节律性标签，这表明以k aiA/B/C为核心振荡器的生物钟系统并不是一种跨物种保守的生物钟系统。近期，人们发现非转录/翻译依赖的振荡器(NTO)也具有成为生物节律性产生和维持的“源动力”的可能。过氧化物氧化还原酶(PRX)氧化还原状态节律性是第一种被报道的跨物种保守的NTO节律性标签，这也日渐成为蓝藻生物钟分子机制研究新的热点。
생물종현상시일충보편존재우생물계세포적내원절률성보지궤제。생물종궤제적존재가이사생물체적대사행위산생병유지이24 h위주기적주야절률，종이경호지괄응우지구자전소산생적배경조건주야간절률성변화。람조시목전생물종분자궤제연구중적모식생물，기의뢰우k ai기인가족성원적핵심생물종조공모식이경피음다연구자상세천명。람조생물종적핵심진탕기시유람조k aiA/B/C적편마산물래조공적，Kai단백적표체모식구유절률성。KaiC단백린산화상태적절률성순배급수입、수출도경상관조성단백적번역후수식상태절률성순배공동조성기반궤회로，부책유지생물종절률성진탕적지속진행병여배경주기보지동보。전통적람조생물종분자궤제모형인위，절률성표체기인번역산물적전록/번역부반궤억제배시생물절률성유지화수출적관건。유감적시，재기타물충생물종분자궤제연구중미발현유kai기인가족성원동원기인조성적절률성표첨，저표명이k aiA/B/C위핵심진탕기적생물종계통병불시일충과물충보수적생물종계통。근기，인문발현비전록/번역의뢰적진탕기(NTO)야구유성위생물절률성산생화유지적“원동력”적가능。과양화물양화환원매(PRX)양화환원상태절률성시제일충피보도적과물충보수적NTO절률성표첨，저야일점성위람조생물종분자궤제연구신적열점。
Circadian clocks are endogenous time-keeping mechanisms which are ubiquitous in a variety of o rganisms from bacteria to mammals. In order to coordinate with and adapt to the daily environmental changes which are driven by the self-rolling of the earth, the circadian clock controls various metabolic and biological activities with a circle period of 24 h. One of the cyanobacterial species, Synechococcus elongatus PCC7942 is a model organism for the circadian clock system. Three proteins encoded by the kaiA/B/C gene cluster, which is functional basis for the circadian rhythm, generate the basic timing loop of the circadian clock in Synechococcus. Circadian time clue is transmitted from the KaiABC-based central oscillator to the clock-controlled transcription factors. KaiC, an autokinase and autophosphatase, is the central component of the cyanobacterial circadian clock. The daily auto-phosphorylation and auto-dephosphorylation cycle of KaiC and the post-translational modification of the proteins, which consisted the inputing and output pathways of the circadian clock, have composed the transcriptional and translational feed-back loop (TTFL). In traditional theory of circadian clock model in cyanobacteria, TTFL regulation of clock genes are thought to be essential for sustaining and outputing of the basic circadian timing loop in Synechococcus. But surprisingly, KaiABC-based central oscillators are only found in cyanobacteria and very few prokaryotic species. It seems that this Kai-based clock is not an ubiquitous time-keeping mechanism that has been selected by organisms during natural evolution. Recently, some circadian clock research groups have demonstrated that non-transcriptional and translational oscillators could be the driving force of the generating and sustaining of biological circadian rhythm. The peroxiredoxins (PRX) are reported to be conserved markers of circadian rhythms, which are also thought to be a new focus of the researches on the molecular mechanism of circadian clock in cyanobacteria.