| Summary: | SepF is identified as a late cell division protein which is conserved among Gram-positive bacteria. It was shown that SepF also has a positive role in formation of FtsZ filaments. Moreover, SepF forms rings by itself and tubules with FtsZ in vitro. Here, it is shown that ring formation is conserved. Several SepF orthologs was purified and studied with electron microscopy. Most of these SepF orthologs polymerized and some of them formed clear rings that are similar to SepF rings of Bacillus subtilis. Furthermore, the C-terminal domain of SepF is sufficient to form SepF rings. The crystal structure of this domain revealed that it forms tight dimers which polymerize through interactions between α-helices. Yeast-two-hybrid studies of SepF mutants showed that the C-terminal domain of SepF is also required for FtsZ interaction. The analysis of the N-terminus of SepF both in vitro and in vivo revealed an amphipathic helix which is crucial for the function of SepF. This study showed that similar to FtsA, SepF anchors FtsZ to the cell membrane. A second project, called Bacillus Minimal Divisome, revealed the core division proteins which are sufficient to initiate the cell division.
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