cheA, cheB, and cheC genes of Escherichia coli and their role in chemotaxis

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Abstract
Motile but generally nonchematotatic (che) mutants of E. coli were isolated by a simple screening method. A total of 172 independent mutants were examined and 4 genes were defined on the basis of mapping and complementation studies. The role of 3 of these genes, cheA, cheB, and cheC, was investigated by determining their null phenotypes with nonsense or bacteriophage Mu-induced mutations. The cheA and cheB products were essential in producing changes of swimming direction and flagellar rotation. The CheC product appeared to be an essential component of the flagellum; specific mutational alterations of this component allowed flagellar assembly but prevented directional changes in swimming. Since some cheB mutants changed directions incessantly, this gene product may also serve to control the direction of flagellar rotation in response to chemoreceptor signals. Most or all of the common elements in the signalling process were involved in the generation and regulation of changes in the direction of flagellar rotation.