Molecular mechanism of sequence-directed DNA loading and translocation by FtsK.
Dimeric circular chromosomes, formed by recombination between monomer sisters, cannot be segregated to daughter cells at cell division. XerCD site-specific recombination at the Escherichia coli dif site converts these dimers to monomers in a reaction that requires the DNA translocase FtsK. Short DNA sequences, KOPS (GGGNAGGG), which are polarized toward dif in the chromosome, direct FtsK translocation. FtsK interacts with KOPS through a C-terminal winged helix domain gamma. The crystal structure of three FtsKgamma domains bound to 8 bp KOPS DNA demonstrates how three gamma domains recognize KOPS. Using covalently linked dimers of FtsK, we infer that three gamma domains per hexamer are sufficient to recognize KOPS and load FtsK and subsequently activate recombination at dif. During translocation, FtsK fails to recognize an inverted KOPS sequence. Therefore, we propose that KOPS act solely as a loading site for FtsK, resulting in a unidirectionally oriented hexameric motor upon DNA.
Löwe
Jan
J
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK. Electronic address: jyl@mrc-lmb.cam.ac.uk.
Ellonen
Antti
A
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Allen
Mark D
MD
Centre for Protein Engineering, MRC, Hills Road, Cambridge CB2 0QH, UK.
Atkinson
Claire
C
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Sherratt
David J
DJ
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Grainge
Ian
I
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. Electronic address: ian.grainge@bioch.ox.ac.uk.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D001681:Biological Assay; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000378:metabolism*; D019281:Dimerization; D006868:Hydrolysis; D008954:Models, Biological; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D011995:Recombination, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D000255:Adenosine Triphosphate