The FtsK γ domain directs oriented DNA translocation by interacting with KOPS

The bacterial septum-located DNA translocase FtsK coordinates circular chromosome segregation with cell division. Rapid translocation of DNA by FtsK is directed by 8-base-pair DNA motifs (KOPS), so that newly replicated termini are brought together at the developing septum, thereby facilitating completion of chromosome segregation. Translocase functions reside in three domains, alpha, beta and gamma. FtsK alpha beta are necessary and sufficient for ATP hydrolysis-dependent DNA translocation, which is modulated by FtsK gamma through its interaction with KOPS. By solving the FtsK gamma structure by NMR, we show that gamma is a winged-helix domain. NMR chemical shift mapping localizes the DNA-binding site on the gamma domain. Mutated proteins with substitutions in the FtsK gamma DNA-recognition helix are impaired in DNA binding and KOPS recognition, yet remain competent in DNA translocation and XerCD-dif site-specific recombination, which facilitates the late stages of chromosome segregation.