Sequence-Directed DNA Translocation by Purified FtsK

Abstract

DNA translocases are molecular motors that move rapidly along DNA using adenosine triphosphate as the source of energy. We directly observed the movement of purified FtsK, an Escherichia coli translocase, on single DNA molecules. The protein moves at 5 kilobases per second and against forces up to 60 piconewtons, and locally reverses direction without dissociation. On three natural substrates, independent of its initial binding position, FtsK efficiently translocates over long distances to the terminal region of the E. coli chromosome, as it does in vivo. Our results imply that FtsK is a bidirectional motor that changes direction in response to short, asymmetric directing DNA sequences.

SpoIIIE strips proteins off the DNA during chromosome translocation

“…In support of the idea that SpoIIIE efficiently strips these proteins off the DNA, in all strains tested the sporulation efficiency was similar to wild type (Supplemental Table S1). These results are consistent with reports that FtsK/SpoIIIE translocases are stronger motors than the replisome Pease et al 2005) and altogether these experiments support the view that the forespore chromosome arrives naked in the developing spore.…”

“…These DNA transporters are polytopic membrane proteins with cytoplasmic ATPase domains. In single molecule experiments, the soluble ATPase domains (the motor domain) of these proteins can translocate along double-stranded DNA at a rate of ∼4-7 kbp/sec (Saleh et al 2004;Pease et al 2005;Ptacin et al 2008). The crystal structure of the cytoplasmic motor domain of FtsK indicates that it assembles into hexameric rings that are large enough to accommodate dsDNA (Massey et al 2006).…”

The bacterial nucleoid: A highly organized and dynamic structure

“…It is still unclear how FtsK determines the direction its substrate has to be translocated to be positioned in the correct daughter cell compartment. A recent single molecule study, however, demonstrated that the sequence of the terminus region is the sole determinant necessary for guiding the protein towards the dif site [Pease et al, 2005]. Directional information could be provided by short repeated sequences identified in the terminal part of the chromosome [Corre and Louarn, 2002], the orientation of which is biased and abruptly changes at dif, thereby pointing toward the site of dimer resolution [Salzberg et al, 1998].…”

The importance of surfaces in single-molecule bioscience

“…21 Forces exerted by different DNA translocating motor proteins have been measured. 66,67 OT measurements have yielded insights into motor enzymes such as kinesin, myosin, and dynein, as well as DNA processing enzymes such as polymerases, nucleases, and helicases [reviewed in ref. 22 ].…”