Tubules, rods and spirals: diverse modes of SepF-FtsZ assembling

Z-ring formation by FtsZ, the master assembler of divisome, is a key step in bacterial cell division. Both formation and membrane anchoring of the Z-ring requires assistance of a number of Z-ring binding proteins, such as FtsA, EzrA, SepF, SepH and ZipA. SepF participates in bundling and membrane anchoring of FtsZ in gram-positive bacteria. We report in vitro biophysical studies of the interactions between FtsZ and cytoplasmic component of cognate SepF from three different bacteria: Mycobacterium tuberculosis , Staphylococcus aureus and Enterococcus gallinarum. While the cytosolic domain of SepF from M. tuberculosis is a dimer, those from S. aureus and E. gallinarum polymerize to form ring-like structures. Mycobacterial SepF helps in bundling of FtsZ filaments to form thick filaments and large spirals. On the other hand, ring-forming SepF from the Firmicutes bundle FtsZ into tubules.