Phosphorelay as the Sole Physiological Route of Signal Transmission by the Arc Two-Component System of Escherichia coli

The Arc two-component system, comprising a tripartite sensor kinase (ArcB) and a response regulator (ArcA), modulates the expression of numerous genes involved in respiratory functions. In this study, the steps of phosphoryl group transfer from phosphorylated ArcB to ArcA were examined in vivo by using single copies of wild-type and mutant arcB alleles. The results indicate that the signal transmission occurs solely by His-Asp-His-Asp phosphorelay.