| FtsZ is a central component of the division apparatus in bacteria. It assembles into a ring-like structure, designated the Z ring. The Z ring assembles at the division site in vivo and determines the division place. The Z ring is normally positioned at midcell and therefore two equal daughter cells are produced.; In a min mutant, the Z ring can also form near a cell pole and a small, spherical, chromosomeless cell (minicell) as well as a short filament are produced. This implies that the min functions to prevent the Z ring from forming at the cell poles. The min system consists of three proteins: MinC, MinD and MinE. MinC is an inhibitor of division that is activated by MinD, a weak ATPase. MinE is thought to bind a hypothetical topological factor at the middle of cell and counteract the activity of the MinCD. As a result, the Z ring forms at midcell while the sites at the cell poles are inhibited.; By constructing a functional GFP-MinC, I found that MinC is a cytoplasmic protein in the absence of other Min proteins. In the presence of MinD, MinC appears on the membrane like MinD itself, indicating that MinD recruits MinC to the membrane. However, in the presence of both MinD and MinE, MinC rapidly oscillates between the halves of the cell.; By constructing a functional MalE-MinC fusion, I found that MinC interacts with FtsZ and prevents polymerization without inhibiting FtsZ's GTPase activity. In contrast, MalE-MmC19 has reduced ability to inhibit division, reduced affinity for FtsZ, and reduced ability to inhibit FtsZ polymerization. Together these results suggest that MinC rapidly oscillates between the poles of the cell to destabilize newly formed FtsZ filaments before they mature into polar Z rings.; In addition, I found that MinC can be split into two functional domains, an N-terminal domain that is responsible for interaction with FtsZ and a C-terminal domain that is responsible for interaction with MinD. I also found that MinC is a dimer and present evidence that both the N-terminal and C-terminal domains are responsible for self-interaction. |
