SpoIIIE

SpoIIIE is a DNA translocase found in Bacillus subtilis and related bacteria. It mediates the translocation of chromosomal DNA from the mother cell into the developing forespore during the late stages of sporulation, enabling complete genome packaging within the forespore.

SpoIIIE belongs to the FtsK-SpoIIIE family of ATPases. The protein contains an N-terminal domain responsible for septal localization and a C-terminal AAA+ ATPase motor that forms a hexameric ring. Together, the ring forms a central pore that couples ATP hydrolysis to directional DNA translocation through the division septum into the forespore. Directionality is guided by interactions with DNA sequence motifs distributed along the chromosome, helping bias translocation toward the forespore.

In the sporulation gene regulatory network, SpoIIIE activity is timed with septation and subsequent activation of forespore-specific sigma factors; this coordination ensures timely genome completion in the forespore. SpoIIIE is essential for efficient sporulation; mutants lacking SpoIIIE exhibit defects in chromosome transfer and reduced sporulation efficiency.

Related systems: SpoIIIE is related to FtsK, a division-associated DNA translocase in Escherichia coli, and shares structural and mechanistic features. The SpoIIIE/FtsK family is conserved across many bacteria and represents a common solution for chromosome translocation during cell division and differentiation.