A two-track model for the spatiotemporal coordination of bacterial septal cell wall synthesis revealed by single-molecule imaging of FtsW

Yang, Xinxing; McQuillen, Ryan; Lyu, Zhixin; Phillips-Mason, Polly J.; Cruz, Ana De La; McCausland, Joshua W.; Liang, Hai; DeMeester, Kristen E.; Santiago, Cintia C.; Grimes, Catherine L.; Boer, Piet A. J. de; Xiao, Jie

doi:10.1038/s41564-020-00853-0

Cited by 57 publications

(136 citation statements)

References 54 publications

(81 reference statements)

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“…In cells depleted of FtsN, the active, slow-moving population of FtsWI on the sPG-track is diminished while the inactive, fast-moving population of FtsWI on the Z-track is enhanced. These findings imply that FtsN activates sPG synthesis, at least in part, by increasing the number of FtsWI molecules on the sPG-track 42 . Whether FtsN accomplishes this by releasing FtsWI from the Z-track or retaining FtsWI on the sPGtrack is not yet known.…”

Section: Introductionmentioning

confidence: 79%

FtsN activates septal cell wall synthesis by forming a processive complex with the septum-specific peptidoglycan synthase in E. coli

Lyu¹,

Yahashiri

Yang

et al. 2021

Preprint

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The FtsN protein of Escherichia coli and other proteobacteria is an essential and highly conserved bitopic membrane protein that triggers the inward synthesis of septal peptidoglycan (sPG) during cell division. Previous work has shown that the activation of sPG synthesis by FtsN involves a series of interactions of FtsN with other divisome proteins and the cell wall. Precisely how FtsN achieves this role is unclear, but a recent study has shown that FtsN promotes the relocation of the essential sPG synthase FtsWI from an FtsZ-associated track (where FtsWI is inactive) to an sPG-track (where FtsWI engages in sPG synthesis). Whether FtsN works by displacing FtsWI from the Z-track or capturing/retaining FtsWI on the sPG-track is not known. Here we use single-molecule imaging and genetic manipulation to investigate the organization and dynamics of FtsN at the septum and how they are coupled to sPG synthesis activity. We found that FtsN exhibits a spatial organization and dynamics distinct from those of the FtsZ-ring. Single FtsN molecules move processively as a single population with a speed of ~ 9 nm s-1, similar to the speed of active FtsWI molecules on the sPG-track, but significantly different from the ~ 30 nm s-1 speed of inactive FtsWI molecules on the FtsZ-track. Furthermore, the processive movement of FtsN is independent of FtsZ's treadmilling dynamics but driven exclusively by active sPG synthesis. Importantly, only the essential domain of FtsN, a three-helix bundle in the periplasm, is required to maintain the processive complex containing both FtsWI and FtsN on the sPG-track. We conclude that FtsN activates sPG synthesis by forming a processive synthesis complex with FtsWI exclusively on the sPG-track. These findings favor a model in which FtsN captures or retains FtsWI on the sPG-track rather than one in which FtsN actively displaces FtsWI from the Z-track.

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Section: Introductionmentioning

confidence: 79%

FtsN activates septal cell wall synthesis by forming a processive complex with the septum-specific peptidoglycan synthase in E. coli

Lyu¹,

Yahashiri

Yang

et al. 2021

Preprint

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“…Two additional mutations were isolated that suppress these inactive FtsL mutations, one in the ECL4 of FtsW (E289G) and one in the pedestal domain of FtsI (K211I). Notably, the ftsW E289G mutation was also isolated as a suppressor of ftsN deletion by other groups [4]. Both of these mutants bypass the essentiality of FtsN indicating that they are active mutants.…”

Section: Plos Geneticsmentioning

confidence: 93%

“…For decades, the class A penicillin binding protein PBP1b (contains both glycosyltransferase and transpeptidase activity) in E. coli was thought to be the primary septal PG synthase [2]. However, recent studies indicate that FtsW is the essential septal PG glycosyltransferase which functions along with its cognate transpeptidase FtsI (PBP3) [3,4], a class B penicillin binding protein. PBP1b contributes to septal PG synthesis, but it is not essential since cells divide relatively normally in its absence [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…However, recent studies indicate that FtsW is the essential septal PG glycosyltransferase which functions along with its cognate transpeptidase FtsI (PBP3) [3,4], a class B penicillin binding protein. PBP1b contributes to septal PG synthesis, but it is not essential since cells divide relatively normally in its absence [4][5][6][7][8][9][10]. FtsW is a member of the SEDS (shape, elongation, division and sporulation) family and is widely conserved in bacteria having a cell wall [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Genetic analysis of the septal peptidoglycan synthase FtsWI complex supports a conserved activation mechanism for SEDS-bPBP complexes

et al. 2021

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SEDS family peptidoglycan (PG) glycosyltransferases, RodA and FtsW, require their cognate transpeptidases PBP2 and FtsI (class B penicillin binding proteins) to synthesize PG along the cell cylinder and at the septum, respectively. The activities of these SEDS-bPBPs complexes are tightly regulated to ensure proper cell elongation and division. In Escherichia coli FtsN switches FtsA and FtsQLB to the active forms that synergize to stimulate FtsWI, but the exact mechanism is not well understood. Previously, we isolated an activation mutation in ftsW (M269I) that allows cell division with reduced FtsN function. To try and understand the basis for activation we isolated additional substitutions at this position and found that only the original substitution produced an active mutant whereas drastic changes resulted in an inactive mutant. In another approach we isolated suppressors of an inactive FtsL mutant and obtained FtsWE289G and FtsIK211I and found they bypassed FtsN. Epistatic analysis of these mutations and others confirmed that the FtsN-triggered activation signal goes from FtsQLB to FtsI to FtsW. Mapping these mutations, as well as others affecting the activity of FtsWI, on the RodA-PBP2 structure revealed they are located at the interaction interface between the extracellular loop 4 (ECL4) of FtsW and the pedestal domain of FtsI (PBP3). This supports a model in which the interaction between the ECL4 of SEDS proteins and the pedestal domain of their cognate bPBPs plays a critical role in the activation mechanism.

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“…The copyright holder for this preprint (which this version posted April 22, 2021. ; https://doi.org/10.1101/2021.04.21.440662 doi: bioRxiv preprint Craven et al: Polar residues in the core of the coiled coil of FtsLB modulate its stability and activation machinery necessary for remodeling the cell wall during the final critical step of cell division [22][23][24][25] .…”

Section: Introductionmentioning

confidence: 99%

The coiled-coil domain ofE. coliFtsLB is a structurally detuned element critical for modulating its activation in bacterial cell division

Craven

Condon

Diaz-Vazquez

et al. 2021

Preprint

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The FtsLB complex is a critical regulator of bacterial cell division, acting as a switch that modulates cell wall reconstruction. Evidence indicates that FtsLB exists in either an off or on state which supports the corresponding activation state of the peptidoglycan synthase complex FtsWI. In Escherichia coli, residues within FtsLB that are critical for this activation are located in a region near the C-terminal end of the periplasmic coiled coil, raising questions about the precise role of this conserved domain in the mechanism. Here, we investigate an unusual cluster of polar amino acids occurring within the core of the coiled coil. These amino acids likely reduce the structural stability of the domain and thus may be important for governing conformational changes. We found that mutating these positions to hydrophobic residues increased the thermal stability of FtsLB but caused cell division defects, suggesting that the coiled-coil domain is an intentionally "detuned" structural element. In addition, suppressor mutations were identified within the polar cluster, indicating that the precise identity of the polar amino acids is important for fine-tuning the structural balance between the off and on states. Based on energetic and sequence propensity considerations, we propose a revised structural model of the tetrameric FtsLB (named the "Y-model") in which the periplasmic domain splits into a pair of coiled-coil branches. In this configuration, the polar amino acids participate in packing within the core, but their hydrophilic terminal moieties remain more favorably exposed to water than in the original four-helix bundle model ("I-model"). The Y-model remains well structured during molecular dynamics simulations, unlike the I-model, and satisfies all known experimental constraints. For this reason, we propose the Y-model as the configuration of the coiled coil of FtsLB and that a shift in this architecture, dependent on its marginal stability, is involved in activating the complex during the process that triggers septal cell wall reconstruction.

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A two-track model for the spatiotemporal coordination of bacterial septal cell wall synthesis revealed by single-molecule imaging of FtsW

Cited by 57 publications

References 54 publications

FtsN activates septal cell wall synthesis by forming a processive complex with the septum-specific peptidoglycan synthase in E. coli

FtsN activates septal cell wall synthesis by forming a processive complex with the septum-specific peptidoglycan synthase in E. coli

Genetic analysis of the septal peptidoglycan synthase FtsWI complex supports a conserved activation mechanism for SEDS-bPBP complexes

The coiled-coil domain ofE. coliFtsLB is a structurally detuned element critical for modulating its activation in bacterial cell division

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