Robustness in an Ultrasensitive Motor
Robustness in an Ultrasensitive Motor
复制标题
超灵敏电机的鲁棒性。
DOI：
10.1128/mbio.03050-19
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发表时间：
2020-03-01
期刊：
影响因子：
6.4
通讯作者：
Yuan, Junhua
中科院分区：
文献类型：
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作者：
Liu, Guangzhe;Tao, Antai;Yuan, Junhua
在大肠杆菌中，趋化反应调节因子Chey-P与位于细菌鞭毛马达底部的开关复合体的一种成分Flim结合，以调节马达的旋转方向。细菌鞭毛马达对细胞质中游离Chey-P的浓度非常敏感。Chey-P与细胞质和马达上的薄膜分子结合。由于FLIM的浓度不可避免地在不同细胞间变化，导致细胞质中游离Chey-P浓度的变化，这就提出了鞭毛马达是否对这种变化具有健壮性的问题，即马达的旋转偏置是否随着FLIM浓度的变化而或多或少地保持恒定。在这里，我们展示了电机对薄膜浓度的变化具有很强的耐用性。我们发现电机的适应性重塑是这种稳健性的机制。随着薄膜分子水平的变化，导致不同数量的未结合的Chey-P分子，马达自适应地改变其开关复合体的组成以补偿这种影响。它的输出，即马达顺时针转动的概率，敏感地取决于输入的Chey-P分子对蛋白质膜(马达开关复合体上的一个成分)的占有率。由于Chey-P分子的细胞池有限，如果不加以补偿，膜水平的细胞间差异将导致电机输出的巨大不必要变化。在这里，我们证明了电机输出对薄膜电平的变化是健壮的，并确定电机开关复合体的自适应重构是这种健壮性的机制。
In Escherichia coli, the chemotaxis response regulator CheY-P binds to FliM, a component of the switch complex at the base of the bacterial flagellar motor, to modulate the direction of motor rotation. The bacterial flagellar motor is ultrasensitive to the concentration of unbound CheY-P in the cytoplasm. CheY-P binds to FliM molecules both in the cytoplasm and on the motor. As the concentration of FliM unavoidably varies from cell to cell, leading to a variation of unbound CheY-P concentration in the cytoplasm, this raises the question whether the flagellar motor is robust against this variation, that is, whether the rotational bias of the motor is more or less constant as the concentration of FliM varies. Here, we showed that the motor is robust against variations of the concentration of FliM. We identified adaptive remodeling of the motor as the mechanism for this robustness. As the level of FliM molecules changes, resulting in different amounts of the unbound CheY-P molecules, the motor adaptively changes the composition of its switch complex to compensate for this effect.IMPORTANCE The bacterial flagellar motor is an ultrasensitive motor. Its output, the probability of the motor turning clockwise, depends sensitively on the occupancy of the protein FliM (a component on the switch complex of the motor) by the input CheY-P molecules. With a limited cellular pool of CheY-P molecules, cell-to-cell variation of the FliM level would lead to large unwanted variation of the motor output if not compensated. Here, we showed that the motor output is robust against the variation of FliM level and identified the adaptive remodeling of the motor switch complex as the mechanism for this robustness.