Figure 8From: Domain swapping reveals that the N-terminal domain of the sensor kinase KdpD in Escherichia coliis important for signalingModel of KdpD activation. KdpD exists in two states, an "OFF" and an "ON" state. Upon stimulus perception, the positively charged surface of the Usp domain within the N-terminal region (yellow) faces the positively charged region (R503-R511) [10, 11, 14] in the C-terminal region of KdpD. Thus, electrostatic repulsions between N- and C-terminal domains force the protein into the "open" position. This in turn releases the N-terminal domain, forming a stable complex with KdpE~P and the DNA [25] initiating kdpFABC expression. Replacement of the KdpD-Usp domain with UspF or UspG results in inversion of the surface net charges. The negative net surface charge of these two proteins forces electrostatic attraction between the N- and the C-terminal regions, leaving KdpD in the "OFF" state under all conditions.Back to article page