Direct interaction between the cell division protein FtsZ and the cell differentiation protein SpoIIE.

SpoIIE is a bifunctional protein with two critical roles in the establishment of cell fate in Bacillus subtilis. First, SpoIIE is needed for the normal formation of the asymmetrically positioned septum that forms early in sporulation and separates the mother cell from the prespore compartment. Secondly, SpoIIE is essential for the activation of the first compartment-specific transcription factor sigma(F) in the prespore. After initiation of sporulation, SpoIIE localizes to the potential asymmetric cell division sites near one or both cell poles. Localization of SpoIIE was shown to be dependent on the essential cell division protein FtsZ. To understand how SpoIIE is targeted to the asymmetric septum we have now analysed its interaction with FtsZ in vitro. Using the yeast two-hybrid system and purified FtsZ, and full-length and truncated SpoIIE proteins, we demonstrate that the two proteins interact directly and that domain II and possibly domain I of SpoIIE are required for the interaction. Moreover, we show that SpoIIE interacts with itself and suggest that this self-interaction plays a role in assembly of SpoIIE into the division machinery.