Tubules, Rods, and Spirals: Diverse Modes of SepF ‐ FtsZ Assembling

ABSTRACT Z‐ring formation by FtsZ, the master assembler of the divisome, is a key step in bacterial cell division. Membrane anchoring of the Z‐ring requires the assistance of dedicated Z‐ring binding proteins, such as SepF and FtsA. 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 a 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 primarily a dimer, those from S. aureus and E. gallinarum polymerize to form ring‐like structures. Mycobacterial SepF helps in the 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. Our results suggest that the oligomeric form of SepF directs how it bundles FtsZ filaments.