Fig. 9.

Z ring formation. (A) The polymerization dynamics of FtsZ have direct implications for Z ring formation in vivo. The MinC background gradient (orange) and NOC lower the polymer bond energy of FtsZ and abolish lateral interactions completely. FtsZ also favorably interacts with membrane-bound ZipA and FtsA. Thus, long filaments are stable only in the midcell region. (B) Simulations show that the Z ring forms with a spontaneous colocalization of FtsZ and ZipA/FtsA. The nascent ring is disordered, with many short filaments in the cell axis direction instead of the circumferential direction. However, through exchange with the cytoplasm, the ring remodels to reach a configuration where most filaments are oriented in the circumferential direction.