Vinella D, D'Ari R
Institut Jacques Monod, CNRS, Université Paris 7, France.
Bioessays. 1995 Jun;17(6):527-36. doi: 10.1002/bies.950170609.
The harmonious growth and cell-to-cell uniformity of steady-state bacterial populations indicate the existence of a well-regulated cell cycle, responding to a set of internal signals. In Escherichia coli, the key events of this cycle are the initiation of DNA replication, nucleoid segregation and the initiation of cell division. The replication initiator is the DnaA protein. In nucleoid segregation, the MukB protein, required for proper partitioning, may be a member of the myosin-kinesin superfamily of mechanoenzymes. In cell division, the FtsZ protein has a tubulin motif, is a GTPase and polymerizes in a ring around midcell during septation; the FtsA protein has an actin-like structure. The nature of the internal signals triggering these events is not known but candidates include cell mass, the superhelical density of the chromosome and the concentration of two regulatory nucleotides, cyclic AMP and ppGpp. The involvement of cytoskeletal-like proteins in key cycle events encourages the notion of a fundamental biological unity in cell cycle regulation in all organisms.
稳态细菌群体的和谐生长及细胞间的一致性表明存在一个调控良好的细胞周期，该周期对一组内部信号作出响应。在大肠杆菌中，这个周期的关键事件是DNA复制起始、类核区分离和细胞分裂起始。复制起始因子是DnaA蛋白。在类核区分离过程中，正确分区所需的MukB蛋白可能是肌球蛋白-驱动蛋白超家族机械酶的一员。在细胞分裂过程中，FtsZ蛋白具有微管蛋白基序，是一种GTP酶，在隔膜形成期间在细胞中部周围聚合成环；FtsA蛋白具有肌动蛋白样结构。触发这些事件的内部信号的本质尚不清楚，但候选信号包括细胞质量、染色体的超螺旋密度以及两种调节核苷酸（环腺苷酸和鸟苷四磷酸）的浓度。细胞骨架样蛋白参与关键周期事件，这支持了所有生物体细胞周期调控存在基本生物学统一性的观点。
