Lele Pushkar P, Shrivastava Abhishek, Roland Thibault, Berg Howard C
Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA. ; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Sci Adv. 2015 Oct 16;1(9):e1500299. doi: 10.1126/sciadv.1500299. eCollection 2015 Oct.
Stimulation of Escherichia coli by exponential ramps of chemoattractants generates step changes in the concentration of the response regulator, CheY-P. Because flagellar motors are ultrasensitive, this should change the fraction of time that motors spin clockwise, the CWbias. However, early work failed to show changes in CWbias when ramps were shallow. This was explained by a model for motor remodeling that predicted plateaus in plots of CWbias versus [CheY-P]. We looked for these plateaus by examining distributions of CWbias in populations of cells with different mean [CheY-P]. We did not find such plateaus. Hence, we repeated the work on shallow ramps and found that motors did indeed respond. These responses were quantitatively described by combining motor remodeling with ultrasensitivity in a model that exhibited high sensitivities over a wide dynamic range.
趋化引诱剂的指数斜坡刺激大肠杆菌会使响应调节因子CheY-P的浓度产生阶跃变化。由于鞭毛马达具有超敏感性，这应该会改变马达顺时针旋转的时间比例，即顺时针偏向（CWbias）。然而，早期研究在斜坡较平缓时未能显示出CWbias的变化。这是由一个马达重塑模型解释的，该模型预测了CWbias与[CheY-P]关系图中的平台期。我们通过检查具有不同平均[CheY-P]的细胞群体中CWbias的分布来寻找这些平台期。我们没有找到这样的平台期。因此，我们重复了关于平缓斜坡的研究，发现马达确实有反应。通过在一个在宽动态范围内表现出高敏感性的模型中结合马达重塑和超敏感性，对这些反应进行了定量描述。
