Investigation of a soluble DNA translocase

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Cells must ensure that duplicated chromosomes are fully separated from each other before cell division occurs. While it is still unclear how eukaryotic cells prevent the entrapment of segregation-delayed chromosomes within the division septum, it has become clear that bacteria contain dedicated DNA translocases that transport DNA through closed membranes if cell division occurs before segregation has been completed. In the case of the model bacterium Bacillus subtilis, we have recently discovered that two DNA translocases perform this task at two different steps. The newly identified SftA DNA translocase moves DNA away during the closure of the division septum, while the membrane protein SpoIIIE pumps DNA through a channel it forms within the closed septum. Interestingly, we found that SftA is fully soluble, and is thus the first non-membrane bound DNA translocase described so far. We plan to investigate how the protein binds to DNA, a question that has not been answered for any DNA translocase. SftA forms hexamers in solution, which somehow must open up for DNA translocation. We will also investigate how the DNA translocation motor of SftA works at a molecular level. We will also analyse how SftA is recruited to the division machinery, which itself is membrane-anchored, through the identification of direct binding partners of SftA.