Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
J Mol Biol. 2013 May 27;425(10):1760-4. doi: 10.1016/j.jmb.2013.02.016. Epub 2013 Feb 26.
The flagellar motor of Escherichia coli adapts to changes in the steady-state level of the chemotaxis response regulator, CheY-P, by adjusting the number of FliM molecules to which CheY-P binds. Previous measurements of motor ultrasensitivity have been made on cells containing different amounts of CheY-P and, thus, different amounts of FliM in flagellar motors. Here, we designed an experiment to measure the sensitivity of motors containing fixed amounts of FliM, finding Hill coefficients about twice as large as those observed before. This ultrasensitivity provides further insights into the motor switching mechanism and plays important roles in chemotaxis signal amplification and coordination of multiple motors. The Hill coefficients observed here appear to be the highest known for allosteric protein complexes, either biological or synthetic. Extreme motor ultrasensitivity broadens our understanding of mechanisms of allostery and serves as an inspiration for future design of synthetic protein switches.
大肠杆菌的鞭毛马达通过调整 CheY-P 结合的 FliM 分子数量来适应化学感应反应调节剂 CheY-P 的稳态水平变化。以前对马达超敏性的测量是在含有不同量 CheY-P 和因此含有不同量 FliM 的鞭毛马达的细胞上进行的。在这里，我们设计了一个实验来测量含有固定量 FliM 的马达的敏感性，发现 Hill 系数大约是以前观察到的两倍。这种超敏性进一步深入了解了马达开关机制，并在化学感应信号放大和多个马达协调中发挥了重要作用。这里观察到的 Hill 系数似乎是所有别构蛋白复合物（无论是生物的还是合成的）中已知的最高值。极端的马达超敏性拓宽了我们对别构机制的理解，并为未来合成蛋白开关的设计提供了灵感。
