The ArcB Sensor Kinase of Escherichia coli: Genetic Exploration of the Transmembrane Region

The Arc two-component signal transduction system of Escherichia coli regulates the expression of numerous operons in response to respiratory growth conditions. Cellular redox state or proton motive force (Δμ̄(H(+))) has been proposed to be the signal for the membrane-associated ArcB sensor kinase. This study provided evidence for a short ArcB periplasmic bridge that contains a His47. The dispensability of this amino acid, the only amino acid with a pK in the physiological range, renders the Δμ̄(H(+)) model unlikely. Furthermore, results from substituting membrane segments of ArcB with counterparts of MalF indicate that the region does not play a stereospecific role in signal reception.