A Defined Terminal Region of the E. coli Chromosome Shows Late Segregation and High FtsK Activity

Self Cite

103

125

Bacteria use the replication origin-to-terminus polarity of their circular chromosomes to control DNA transactions during the cell cycle. Segregation starts by active migration of the region of origin followed by progressive movement of the rest of the chromosomes. The last steps of segregation have been studied extensively in the case of dimeric sister chromosomes and when chromosome organization is impaired by mutations. In these special cases, the divisome-associated DNA translocase FtsK is required. FtsK pumps chromosomes toward the dif chromosome dimer resolution site using polarity of the FtsK-orienting polar sequence (KOPS) DNA motifs. Assays based on monitoring dif recombination have suggested that FtsK acts only in these special cases and does not act on monomeric chromosomes. Using a two-color system to visualize pairs of chromosome loci in living cells, we show that the spatial resolution of sister loci is accurately ordered from the point of origin to the dif site. Furthermore, ordered segregation in a region ∼200 kb long surrounding dif depended on the oriented translocation activity of FtsK but not on the formation of dimers or their resolution. FtsK-mediated segregation required the MatP protein, which delays segregation of the dif-surrounding region until cell division. We conclude that FtsK segregates the terminus region of sister chromosomes whether they are monomeric or dimeric and does so in an accurate and ordered manner. Our data are consistent with a model in which FtsK acts to release the MatP-mediated cohesion and/or interaction with the division apparatus of the terminus region in a KOPS-oriented manner.

Section: Resultsmentioning

confidence: 99%

“…FtsK, a DNA translocase associated with the divisome, is also required (13,14). FtsK acts in a region about 400 kb long (15) and translocates DNA toward dif. Translocation is oriented by recognition of the FtsK-orienting polar sequences (KOPS) DNA motifs that are preferentially oriented toward dif, particularly in the ter region (4,(16)(17)(18).…”

mentioning

confidence: 99%

FtsK actively segregates sister chromosomes in Escherichia coli

Stouf

Meile

Cornet

2013

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103

125

“…This geometry would seemingly preclude FtsK from undergoing a free diffusive search throughout the bacterial genome, and therefore we envision that FtsK searches for KOPS through a mechanism involving random sampling of the DNA as the genome is being pulled through the division septum. The dif activation zone of the chromosome encompasses a ≈400-kb segment within the terminus region and contains a total of 34 KOPS sites in the correct orientation to direct FtsK toward dif (30). This large number of sites could help ensure that FtsK engages KOPS.…”

Section: Model For Kops-specific Loading Of Ftsk In the Absence Of Atpmentioning

confidence: 99%

Single-molecule imaging of DNA curtains reveals mechanisms of KOPS sequence targeting by the DNA translocase FtsK

Lee¹,

Finkelstein²,

Crozat

et al. 2012

FtsK is a hexameric DNA translocase that participates in the final stages of bacterial chromosome segregation. Here we investigate the DNA-binding and translocation activities of FtsK in real time by imaging fluorescently tagged proteins on nanofabricated curtains of DNA. We show that FtsK preferentially loads at 8-bp KOPS (FtsK Orienting Polar Sequences) sites and that loading is enhanced in the presence of ADP. We also demonstrate that FtsK locates KOPS through a mechanism that does not involve extensive 1D diffusion at the scale of our resolution. Upon addition of ATP, KOPS-bound FtsK translocates in the direction dictated by KOPS polarity, and once FtsK has begun translocating it does not rerecognize KOPS from either direction. However, FtsK can abruptly change directions while translocating along DNA independent of KOPS, suggesting that the ability to reorient on DNA does not arise from DNA sequence-specific effects. Taken together, our data support a model in which FtsK locates KOPS through random collisions, preferentially engages KOPS in the ADP-bound state, translocates in the direction dictated by the polar orientation of KOPS, and is incapable of recognizing KOPS while translocating along DNA.

“…Some of these Zaps connect the Z-ring to the bacterial chromosome through a multilayered protein network that includes the chromosome-binding protein MatP (16)(17)(18)(19). Together with FtsK, a divisome protein involved in chromosome segregation and dimer resolution (20)(21)(22)(23)(24)(25), this group of proteins likely plays a role in coordinating cell envelope invagination with chromosome segregation (16,18,26). Thus, the divisome consists of three interacting components: the Z-ring, PG-linked proteins, and chromosome-linked proteins.…”

mentioning

confidence: 99%

Defining the rate-limiting processes of bacterial cytokinesis

Coltharp

Buss

Plumer

et al. 2016

152

205

Bacterial cytokinesis is accomplished by the essential ‘divisome’ machinery. The most widely conserved divisome component, FtsZ, is a tubulin homolog that polymerizes into the ‘FtsZ-ring’ (‘Z-ring’). Previous in vitro studies suggest that Z-ring contraction serves as a major constrictive force generator to limit the progression of cytokinesis. Here, we applied quantitative superresolution imaging to examine whether and how Z-ring contraction limits the rate of septum closure during cytokinesis in Escherichia coli cells. Surprisingly, septum closure rate was robust to substantial changes in all Z-ring properties proposed to be coupled to force generation: FtsZ’s GTPase activity, Z-ring density, and the timing of Z-ring assembly and disassembly. Instead, the rate was limited by the activity of an essential cell wall synthesis enzyme and further modulated by a physical divisome–chromosome coupling. These results challenge a Z-ring–centric view of bacterial cytokinesis and identify cell wall synthesis and chromosome segregation as limiting processes of cytokinesis.