The ArcB sensor kinase of Escherichia coli: Genetic exploration of the transmembrane region

The Arc two-component signal transduction system of Escherichia coli regula tes the expression of numerous operons in response to respiratory growth co nditions. Cellular redox state or proton motive force (Delta<(mu)over bar>( H+)) has been proposed to be the signal for the membrane-associated ArcB se nsor kinase. This study provided evidence for a short ArcB periplasmic brid ge that contains a His47. The dispensability of this amino acid, the only a mino acid with a pK in the physiological range, renders the Delta<(mu)over bar>(H+) model unlikely. Furthermore, results from substituting membrane se gments of ArcB with counterparts of MalF indicate that the region does not play a stereospecific role in signal reception.