Examination of the Interaction Between FtsZ and MinCN in E. Coli Suggests How MinC Disrupts Z Rings

In Escherichia coli the Min system prevents Z ring assembly at cell poles by topologically regulating the division inhibitor MinC. The MinC protein has two domains of equal size and both domains can target FtsZ and block cell division in the proper context. Recently, we have shown that, along with MinD, the C-terminal domain of MinC (MinC(C)) competes with FtsA, and to a lesser extent with ZipA, for interaction with the C-terminal tail of FtsZ to block division. Here we explored the interaction between the N-terminal domain of MinC (MinC(N)) and FtsZ. A search for mutations in ftsZ that confer resistance to MinC(N) identified an alpha-helix at the interface of FtsZ subunits as being critical for the activity of MinC(N). Focusing on one such mutant FtsZ-N280D, we showed that it greatly reduced the FtsZ-MinC interaction and was resistant to MinC(N) both in vivo and in vitro. With these results, an updated model for the action of MinC on FtsZ is proposed: MinC interacts with FtsZ to disrupt two interactions, FtsZ-FtsA/ZipA and FtsZ-FtsZ, both of which are essential for Z ring formation.