Imae Y, Mizuno T, Maeda K
J Bacteriol. 1984 Jul;159(1):368-74. doi: 10.1128/jb.159.1.368-374.1984.
Methyl-accepting chemotaxis protein-methyltransferase-deficient mutants, cheR mutants, of Escherichia coli showed a tumble response to repellents only at low temperatures, and the resultant tumbling lasted unless the condition was changed. The swimming pattern of the repellent-treated cells was different at different temperatures, indicating that the absolute temperature is a determinant of the tumbling frequency of those cells. The tumbling of those cells was also suppressed by the addition of attractants. Under a suitable repellent concentration, the tumbling frequency of the cells was found to be simply determined by the ligand occupancy of chemoreceptors for many attractants. In a methyl-accepting chemotaxis protein-methylesterase-deficient mutant, a cheB deletion mutant, the tumbling frequency was also determined by receptor occupancy of some attractants. These results indicate that in the adaptation-deficient mutants, sensory signals are produced in proportion to the amount of ligand-bound or of thermally altered receptors and transmitted to the flagellar motors without any modification. Thus, it is concluded that the adaptation system, namely, the methylation-demethylation system of methyl-accepting chemotaxis proteins, is not concerned with the step of chemosensory or thermosensory excitation. A simple model is proposed to explain how the swimming pattern of the adaptation-deficient mutants is determined.
大肠杆菌的甲基化趋化蛋白 - 甲基转移酶缺陷型突变体（cheR突变体）仅在低温下对驱避剂表现出翻滚反应，并且除非条件改变，否则由此产生的翻滚会持续。经驱避剂处理的细胞在不同温度下的游动模式不同，这表明绝对温度是这些细胞翻滚频率的一个决定因素。添加引诱剂也会抑制这些细胞的翻滚。在合适的驱避剂浓度下，发现许多引诱剂作用下细胞的翻滚频率仅由化学感受器的配体占有率简单决定。在甲基化趋化蛋白 - 甲酯酶缺陷型突变体（cheB缺失突变体）中，翻滚频率也由一些引诱剂的受体占有率决定。这些结果表明，在适应缺陷型突变体中，感觉信号与结合配体或热改变的受体数量成比例产生，并在没有任何修饰的情况下传递到鞭毛马达。因此，可以得出结论，适应系统，即甲基化趋化蛋白的甲基化 - 去甲基化系统，与化学感觉或热感觉激发步骤无关。提出了一个简单模型来解释适应缺陷型突变体的游动模式是如何确定的。
