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

Area of Science:

• Molecular Biology
• Microbiology
• Structural Biology

Background:

• The bacterial FtsK protein is a DNA translocase essential for coordinating chromosome segregation with cell division.
• FtsK function relies on recognizing specific DNA motifs (KOPS) to direct DNA translocation to the cell septum.
• FtsK comprises three domains: alpha, beta, and gamma, with distinct roles in DNA translocation and regulation.

Purpose of the Study:

• To elucidate the structural and functional role of the FtsKgamma domain in DNA binding and KOPS recognition.
• To investigate how FtsKgamma interacts with DNA and modulates FtsK activity.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the three-dimensional structure of the FtsKgamma domain.
• NMR chemical shift mapping was employed to identify the DNA-binding interface on FtsKgamma.
• Site-directed mutagenesis was performed to alter residues within the putative DNA-recognition helix of FtsKgamma.

Main Results:

• The FtsKgamma domain was determined to be a winged-helix DNA-binding domain.
• NMR mapping identified the DNA-binding site located on the gamma domain's recognition helix.
• Mutations in the FtsKgamma DNA-recognition helix impaired DNA and KOPS binding but did not affect DNA translocation or XerCD-dif recombination.

Conclusions:

• The FtsKgamma domain is crucial for specific DNA recognition, particularly KOPS motifs.
• While FtsKgamma mediates DNA binding, the FtsKalphabeta domains are sufficient for ATP-dependent translocation.
• These findings highlight the modular nature of FtsK and the distinct roles of its domains in orchestrating chromosome segregation.