Fuhrer D K, Ordal G W
Department of Biochemistry, College of Medicine, University of Illinois, Urbana 61801.
J Bacteriol. 1991 Dec;173(23):7443-8. doi: 10.1128/jb.173.23.7443-7448.1991.
The Bacillus subtilis cheN gene was isolated, sequenced, and expressed. It encodes a large negatively charged protein with a molecular weight of approximately 74,000. The predicted protein sequence has 33 to 34% identity with the Escherichia coli and Salmonella typhimurium CheA and Myxococcus xanthus FrzE sequences. These proteins are found to autophosphorylate and are members of the same histidine kinase signal modulating family. CheN has several conserved regions (including the histidine that is phosphorylated in CheA) that coincide with other autophosphorylated signal transducers. A null mutant is defective in attractant-induced methanol formation and shows no behavioral response to chemoeffectors. These results imply that in B. subtilis the mechanism of chemotaxis involves phosphoryl transfer similar to that in E. coli. However, the CheN null mutant mostly tumbles, whereas CheA mutants swim smoothly, and only in B. subtilis does excitation lead to methyl transfer and methanol formation. Thus, the overall mechanism of chemotaxis is different in the two organisms.
枯草芽孢杆菌的cheN基因被分离、测序并表达。它编码一种分子量约为74,000的带大量负电荷的蛋白质。预测的蛋白质序列与大肠杆菌、鼠伤寒沙门氏菌的CheA以及粘球菌的FrzE序列有33%至34%的同源性。这些蛋白质被发现可进行自身磷酸化，并且是同一组氨酸激酶信号调节家族的成员。CheN有几个保守区域（包括在CheA中被磷酸化的组氨酸），这些区域与其他自身磷酸化的信号转导器一致。一个缺失突变体在引诱剂诱导的甲醇形成方面存在缺陷，并且对化学效应物没有行为反应。这些结果表明，在枯草芽孢杆菌中，趋化作用机制涉及类似于大肠杆菌中的磷酸转移。然而，CheN缺失突变体大多发生翻滚，而CheA突变体则能平稳游动，并且只有在枯草芽孢杆菌中，兴奋才会导致甲基转移和甲醇形成。因此，这两种生物体中的趋化作用总体机制是不同的。
