Non-essential, abundant cell division factor that is required for proper Z-ring formation. It is recruited early to the divisome by direct interaction with FtsZ, stimulating Z-ring assembly and thereby promoting cell division earlier in the cell cycle. Its recruitment to the Z-ring requires functional FtsA or ZipA. Homodimer. The ends of the coiled-coil dimer bind to each other, forming polymers. Interacts with FtsZ. Localizes to the septum at mid-cell, in a FtsZ-like pattern. Belongs to the ZapB family.