Stock J B, Maderis A M, Koshland D E
Cell. 1981 Nov;27(1 Pt 2):37-44. doi: 10.1016/0092-8674(81)90358-5.
Although chemoreceptor methylation in Salmonella typhimurium and Escherichia coli has been shown to be at the core of the chemotactic phenomenon, mutants in the gene (cheR) that codes for the methylating enzyme still respond and adapt to repellent stimuli. Analyses of receptor methylation and transferase activity show that this behavior is not due to residual transferase activity. That receptor methylation is not absolutely required for chemotactic sensory processing is confirmed by the isolation of cheR pseudorevertants that remain defective in receptor methylation, yet are able to respond to gradients on semi-solid tryptone agar. A detailed comparison of cheR and wild-type responses indicates that chemotaxis is mediated by at least two interdependent adaptation systems, only one of which involves receptor methylation. The interaction of these two systems produces the full response in wild-type cells. Methylation-deficient mutants exhibit a partial response and retain some chemotactic ability.
尽管已证明鼠伤寒沙门氏菌和大肠杆菌中的化学感受器甲基化是趋化现象的核心，但编码甲基化酶的基因（cheR）中的突变体仍能对驱避刺激做出反应并适应。对受体甲基化和转移酶活性的分析表明，这种行为并非由于残留的转移酶活性。通过分离在受体甲基化方面仍然存在缺陷但能够对半固体胰蛋白胨琼脂上的梯度做出反应的cheR假回复突变体，证实了趋化感觉处理并非绝对需要受体甲基化。对cheR和野生型反应的详细比较表明，趋化作用至少由两个相互依赖的适应系统介导，其中只有一个涉及受体甲基化。这两个系统的相互作用在野生型细胞中产生完整的反应。甲基化缺陷突变体表现出部分反应并保留一些趋化能力。
