The keepers of the ring: regulators of FtsZ assembly

FtsZ, a GTPase distributed in the cytoplasm of most bacteria, is the major component of the machinery responsible for division (the divisome) in Escherichia coli. It interacts with additional proteins that contribute to its function forming a ring at the midcell that is essential to constrict the membrane. FtsZ is indirectly anchored to the membrane and it is prevented from polymerizing at locations where septation is undesired. Several properties of FtsZ are mediated by other proteins that function as keepers of the ring. ZipA and FtsA serve to anchor the ring, and together with a set of Zap proteins, they stabilize it. The MinCDE and SlmA proteins prevent the polymerization of FtsZ at sites other than the midcell. Finally, ClpP degrades FtsZ, an action prevented by ZipA. Many of the FtsZ keepers interact with FtsZ through a central hub located at its carboxy terminal end.