Regulation of the Peptidoglycan Polymerase Activity of PBP1b by Antagonist Actions of the Core Divisome Proteins FtsBLQ and FtsN

ABSTRACTPeptidoglycan (PG) is an essential constituent of the bacterial cell wall. During cell division, PG synthesis localizes at midcell under the control of a multiprotein complex, the divisome, allowing the safe formation of two new cell poles and separation of daughter cells. Genetic studies inEscherichia colipointed out that FtsBLQ and FtsN participate in the regulation of septal PG (sPG) synthesis; however, the underlying molecular mechanisms remained largely unknown. Here we show that FtsBLQ subcomplex directly interacts with the PG synthase PBP1b and with the subcomplex FtsW-PBP3, mainly via FtsW. Strikingly, we discovered that FtsBLQ inhibits the glycosyltransferase activity of PBP1b and that this inhibition was antagonized by the PBP1b activators FtsN and LpoB. The same results were obtained in the presence of FtsW-PBP3. Moreover, using a simple thioester substrate (S2d), we showed that FtsBLQ also inhibits the transpeptidase domain of PBP3 but not of PBP1b. As the glycosyltransferase and transpeptidase activities of PBP1b are coupled and PBP3 activity requires nascent PG substrate, the results suggest that PBP1b inhibition by FtsBLQ will block sPG synthesis by these enzymes, thus maintaining cell division as repressed until the maturation of the divisome is signaled by the accumulation of FtsN, which triggers sPG synthesis and the initiation of cell constriction. These results confirm that PBP1b plays an important role inE. colicell division and shed light on the specific role of FtsN, which seems to counterbalance the inhibitory effect of FtsBLQ to restore PBP1b activity.IMPORTANCEBacterial cell division is governed by a multiprotein complex called divisome, which facilitates a precise cell wall synthesis at midcell and daughter cell separation. Protein-protein interactions and activity studies using different combinations of the septum synthesis core of the divisome revealed that the glycosyltransferase activity of PBP1b is repressed by FtsBLQ and that the presence of FtsN or LpoB suppresses this inhibition. Moreover, FtsBLQ also inhibits the PBP3 activity on a thioester substrate. These results provide enzymatic evidence of the regulation of the peptidoglycan synthase PBP1b and PBP3 within the divisome. The results confirm that PBP1b plays an important role inE. colicell division and shed light on the specific role of FtsN, which functions to relieve the repression on PBP1b by FtsBLQ and to initiate septal peptidoglycan synthesis.

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FtsW exhibits distinct processive motions driven by either septal cell wall synthesis or FtsZ treadmilling in E. coli

10.1101/850073 ◽

2019 ◽

Cited By ~ 8

Author(s):

Xinxing Yang ◽

Ryan McQuillen ◽

Zhixin Lyu ◽

Polly Phillips-Mason ◽

Ana De La Cruz ◽

...

Keyword(s):

Cell Wall ◽

Cell Division ◽

Single Molecule ◽

Bacterial Cell ◽

Spatial Information ◽

Bacterial Species ◽

E Coli ◽

Slow Moving

AbstractDuring bacterial cell division, synthesis of new septal peptidoglycan (sPG) is crucial for successful cytokinesis and cell pole morphogenesis. FtsW, a SEDS (Shape, Elongation, Division and Sporulation) family protein and an indispensable component of the cell division machinery in all walled bacterial species, was recently identified in vitro as a new monofunctional peptidoglycan glycosyltransferase (PGTase). FtsW and its cognate monofunctional transpeptidase (TPase) class B penicillin binding protein (PBP3 or FtsI in E. coli) may constitute the essential, bifunctional sPG synthase specific for new sPG synthesis. Despite its importance, the septal PGTase activity of FtsW has not been documented in vivo. How its activity is spatiotemporally regulated in vivo has also remained unknown. Here we investigated the septal PGTase activity and dynamics of FtsW in E. coli cells using a combination of single-molecule imaging and genetic manipulations. We show that FtsW exhibits robust activity to incorporate an N-acetylmuramic acid analog at septa in the absence of other known PGTases, confirming FtsW as the essential septum-specific PGTase in vivo. Notably, we identified two populations of processive moving FtsW molecules at septa. A fast-moving population is driven by the treadmilling dynamics of FtsZ and independent of sPG synthesis. A slow-moving population is driven by active sPG synthesis and independent of FtsZ’s treadmilling dynamics. We further identified that FtsN, a potential sPG synthesis activator, plays an important role in promoting the slow-moving, sPG synthesis-dependent population. Our results support a two-track model, in which inactive sPG synthase molecules follow the fast treadmilling “Z-track” to be distributed along the septum; FtsN promotes their release from the “Z-track” to become active in sPG synthesis on the slow “sPG-track”. This model explains how the spatial information is integrated into the regulation of sPG synthesis activity and suggests a new mechanistic framework for the spatiotemporal coordination of bacterial cell wall constriction.

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Localization, Assembly, and Activation of the Escherichia coli Cell Division Machinery

EcoSal Plus ◽

10.1128/ecosalplus.esp-0022-2021 ◽

2021 ◽

Author(s):

Petra Anne Levin ◽

Anuradha Janakiraman

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Bacterial Cell ◽

Coli Cell ◽

Bacterial Cell Division ◽

Content Type ◽

E Coli ◽

Insight Into

Decades of research, much of it in Escherichia coli , have yielded a wealth of insight into bacterial cell division. Here, we provide an overview of the E. coli division machinery with an emphasis on recent findings.

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Alginate Polymerization and Modification Are Linked in Pseudomonas aeruginosa

mBio ◽

10.1128/mbio.00453-15 ◽

2015 ◽

Vol 6 (3) ◽

Cited By ~ 33

Author(s):

M. Fata Moradali ◽

Ivan Donati ◽

Ian M. Sims ◽

Shirin Ghods ◽

Bernd H. A. Rehm

Keyword(s):

Pseudomonas Aeruginosa ◽

Material Properties ◽

Molecular Mechanisms ◽

Cell Aggregation ◽

Activation Mechanism ◽

Cellulose Synthesis ◽

Multiprotein Complex ◽

Site Specific ◽

Content Type

ABSTRACTThe molecular mechanisms of alginate polymerization/modification/secretion by a proposed envelope-spanning multiprotein complex are unknown. Here, bacterial two-hybrid assays and pulldown experiments showed that the catalytic subunit Alg8 directly interacts with the proposed copolymerase Alg44 while embedded in the cytoplasmic membrane. Alg44 additionally interacts with the lipoprotein AlgK bridging the periplasmic space. Site-specific mutagenesis of Alg44 showed that protein-protein interactions and stability were independent of conserved amino acid residues R17 and R21, which are involved in c-di-GMP binding, the N-terminal PilZ domain, and the C-terminal 26 amino acids. Site-specific mutagenesis was employed to investigate the c-di-GMP-mediated activation of alginate polymerization by the PilZAlg44domain and Alg8. Activation was found to be different from the proposed activation mechanism for cellulose synthesis. The interactive role of Alg8, Alg44, AlgG (epimerase), and AlgX (acetyltransferase) on alginate polymerization and modification was studied by using site-specific deletion mutants, inactive variants, and overproduction of subunits. The compositions, molecular masses, and material properties of resulting novel alginates were analyzed. The molecular mass was reduced by epimerization, while it was increased by acetylation. Interestingly, when overproduced, Alg44, AlgG, and the nonepimerizing variant AlgG(D324A) increased the degree of acetylation, while epimerization was enhanced by AlgX and its nonacetylating variant AlgX(S269A). Biofilm architecture analysis showed that acetyl groups promoted cell aggregation while nonacetylated polymannuronate alginate promoted stigmergy. Overall, this study sheds new light on the arrangement of the multiprotein complex involved in alginate production. Furthermore, the activation mechanism and the interplay between polymerization and modification of alginate were elucidated.IMPORTANCEThis study provides new insights into the molecular mechanisms of the synthesis of the unique polysaccharide, alginate, which not only is an important virulence factor of the opportunistic human pathogenPseudomonas aeruginosabut also has, due to its material properties, many applications in medicine and industry. Unraveling the assembly and composition of the alginate-synthesizing and envelope-spanning multiprotein complex will be of tremendous significance for the scientific community. We identified a protein-protein interaction network inside the multiprotein complex and studied its relevance with respect to alginate polymerization/modification as well as the c-di-GMP-mediated activation mechanism. A relationship between alginate polymerization and modification was shown. Due to the role of alginate in pathogenesis as well as its unique material properties harnessed in numerous applications, results obtained in this study will aid the design and development of inhibitory drugs as well as the commercial bacterial production of tailor-made alginates.

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Structure and Mutational Analyses of Escherichia coli ZapD Reveal Charged Residues Involved in FtsZ Filament Bundling

Journal of Bacteriology ◽

10.1128/jb.00969-15 ◽

2016 ◽

Vol 198 (11) ◽

pp. 1683-1693 ◽

Cited By ~ 8

Author(s):

Elyse J. Roach ◽

Charles Wroblewski ◽

Laura Seidel ◽

Alison M. Berezuk ◽

Dyanne Brewer ◽

...

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Bacterial Cell ◽

Site Directed Mutagenesis ◽

Bacterial Cell Division ◽

Wild Type ◽

Content Type ◽

E Coli ◽

Z Ring

ABSTRACTBacterial cell division is an essential and highly coordinated process. It requires the polymerization of the tubulin homologue FtsZ to form a dynamic ring (Z-ring) at midcell. Z-ring formation relies on a group of FtsZ-associatedproteins (Zap) for stability throughout the process of division. InEscherichia coli, there are currently five Zap proteins (ZapA through ZapE), of which four (ZapA, ZapB, ZapC, and ZapD) are small soluble proteins that act to bind and bundle FtsZ filaments. In particular, ZapD forms a functional dimer and interacts with the C-terminal tail of FtsZ, but little is known about its structure and mechanism of action. Here, we present the crystal structure ofEscherichia coliZapD and show it forms a symmetrical dimer with centrally located α-helices flanked by β-sheet domains. Based on the structure of ZapD and its chemical cross-linking to FtsZ, we targeted nine charged ZapD residues for modification by site-directed mutagenesis. Usingin vitroFtsZ sedimentation assays, we show that residues R56, R221, and R225 are important for bundling FtsZ filaments, while transmission electron microscopy revealed that altering these residues results in different FtsZ bundle morphology compared to those of filaments bundled with wild-type ZapD. ZapD residue R116 also showed altered FtsZ bundle morphology but levels of FtsZ bundling similar to that of wild-type ZapD. Together, these results reveal that ZapD residues R116, R221, and R225 likely participate in forming a positively charged binding pocket that is critical for bundling FtsZ filaments.IMPORTANCEZ-ring assembly underpins the formation of the essential cell division complex known as the divisome and is required for recruitment of downstream cell division proteins. ZapD is one of several proteins inE. colithat associates with the Z-ring to promote FtsZ bundling and aids in the overall fitness of the division process. In the present study, we describe the dimeric structure ofE. coliZapD and identify residues that are critical for FtsZ bundling. Together, these results advance our understanding about the formation and dynamics of the Z-ring prior to bacterial cell division.

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The Chaperonin GroESL Facilitates Caulobacter crescentus Cell Division by Supporting the Functions of the Z-Ring Regulators FtsA and FzlA

mBio ◽

10.1128/mbio.03564-20 ◽

2021 ◽

Vol 12 (3) ◽

Author(s):

Kristen Schroeder ◽

Kristina Heinrich ◽

Ines Neuwirth ◽

Kristina Jonas

Keyword(s):

Cell Cycle ◽

Cell Wall ◽

Cell Division ◽

Bacterial Cell ◽

Antimicrobial Agents ◽

Caulobacter Crescentus ◽

Content Type ◽

Growing Cell ◽

Z Ring ◽

Bacterial Cell Cycle

ABSTRACT The highly conserved chaperonin GroESL performs a crucial role in protein folding; however, the essential cellular pathways that rely on this chaperone are underexplored. Loss of GroESL leads to severe septation defects in diverse bacteria, suggesting the folding function of GroESL may be integrated with the bacterial cell cycle at the point of cell division. Here, we describe new connections between GroESL and the bacterial cell cycle using the model organism Caulobacter crescentus. Using a proteomics approach, we identify candidate GroESL client proteins that become insoluble or are degraded specifically when GroESL folding is insufficient, revealing several essential proteins that participate in cell division and peptidoglycan biosynthesis. We demonstrate that other cell cycle events, such as DNA replication and chromosome segregation, are able to continue when GroESL folding is insufficient. We further find that deficiency of two FtsZ-interacting proteins, the bacterial actin homologue FtsA and the constriction regulator FzlA, mediate the GroESL-dependent block in cell division. Our data show that sufficient GroESL is required to maintain normal dynamics of the FtsZ scaffold and divisome functionality in C. crescentus. In addition to supporting divisome function, we show that GroESL is required to maintain the flow of peptidoglycan precursors into the growing cell wall. Linking a chaperone to cell division may be a conserved way to coordinate environmental and internal cues that signal when it is safe to divide. IMPORTANCE All organisms depend on mechanisms that protect proteins from misfolding and aggregation. GroESL is a highly conserved molecular chaperone that functions to prevent protein aggregation in organisms ranging from bacteria to humans. Despite detailed biochemical understanding of GroESL function, the in vivo pathways that strictly depend on this chaperone remain poorly defined in most species. This study provides new insights into how GroESL is linked to the bacterial cell division machinery, a crucial target of current and future antimicrobial agents. We identify a functional interaction between GroESL and the cell division proteins FzlA and FtsA, which modulate Z-ring function. FtsA is a conserved bacterial actin homologue, suggesting that as in eukaryotes, some bacteria exhibit a connection between cytoskeletal actin proteins and chaperonins. Our work further defines how GroESL is integrated with cell wall synthesis and illustrates how highly conserved folding machines ensure the functioning of fundamental cellular processes during stress.

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DrpB (YedR) Is a Nonessential Cell Division Protein in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00284-20 ◽

2020 ◽

Vol 202 (23) ◽

Author(s):

Atsushi Yahashiri ◽

Jill T. Babor ◽

Ariel L. Anwar ◽

Ryan P. Bezy ◽

Evan W. Piette ◽

...

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Ionic Strength ◽

Bacterial Cell ◽

Enteric Bacteria ◽

High Ionic Strength ◽

Bacterial Cell Division ◽

Content Type ◽

E Coli ◽

Low Ionic Strength

ABSTRACT We report that the small Escherichia coli membrane protein DrpB (formerly YedR) is involved in cell division. We discovered DrpB in a screen for multicopy suppressors of a ΔftsEX mutation that prevents divisome assembly when cells are plated on low ionic strength medium, such as lysogeny broth without NaCl. Characterization of DrpB revealed that (i) translation initiates at an ATG annotated as codon 22 rather than the GTG annotated as codon 1, (ii) DrpB localizes to the septal ring when cells are grown in medium of low ionic strength but localization is greatly reduced in medium of high ionic strength, (iii) overproduction of DrpB in a ΔftsEX mutant background improves recruitment of the septal peptidoglycan synthase FtsI, implying multicopy suppression works by rescuing septal ring assembly, (iv) a ΔdrpB mutant divides quite normally, but a ΔdrpB ΔdedD double mutant has a strong division and viability defect, albeit only in medium of high ionic strength, and (v) DrpB homologs are found in E. coli and a few closely related enteric bacteria, but not outside this group. In sum, DrpB is a poorly conserved nonessential division protein that improves the efficiency of cytokinesis under suboptimal conditions. Proteins like DrpB are likely to be a widespread feature of the bacterial cell division apparatus, but they are easily overlooked because mutants lack obvious shape defects. IMPORTANCE A thorough understanding of bacterial cell division requires identifying and characterizing all of the proteins that participate in this process. Our discovery of DrpB brings us one step closer to this goal in E. coli.

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A New Essential Cell Division Protein in Caulobacter crescentus

Journal of Bacteriology ◽

10.1128/jb.00811-16 ◽

2017 ◽

Vol 199 (8) ◽

Cited By ~ 3

Author(s):

Aurora Osorio ◽

Laura Camarena ◽

Miguel Angel Cevallos ◽

Sebastian Poggio

Keyword(s):

Cell Division ◽

Bacterial Cell ◽

Caulobacter Crescentus ◽

Accessory Proteins ◽

Multiprotein Complex ◽

Bacterial Cell Division ◽

Content Type ◽

Division Site ◽

Complex Process ◽

Cell Division Protein

ABSTRACT Bacterial cell division is a complex process that relies on a multiprotein complex composed of a core of widely conserved and generally essential proteins and on accessory proteins that vary in number and identity in different bacteria. The assembly of this complex and, particularly, the initiation of constriction are regulated processes that have come under intensive study. In this work, we characterize the function of DipI, a protein conserved in Alphaproteobacteria and Betaproteobacteria that is essential in Caulobacter crescentus. Our results show that DipI is a periplasmic protein that is recruited late to the division site and that it is required for the initiation of constriction. The recruitment of the conserved cell division proteins is not affected by the absence of DipI, but localization of DipI to the division site occurs only after a mature divisome has formed. Yeast two-hybrid analysis showed that DipI strongly interacts with the FtsQLB complex, which has been recently implicated in regulating constriction initiation. A possible role of DipI in this process is discussed. IMPORTANCE Bacterial cell division is a complex process for which most bacterial cells assemble a multiprotein complex that consists of conserved proteins and of accessory proteins that differ among bacterial groups. In this work, we describe a new cell division protein (DipI) present only in a group of bacteria but essential in Caulobacter crescentus. Cells devoid of DipI cannot constrict. Although a mature divisome is required for DipI recruitment, DipI is not needed for recruiting other division proteins. These results, together with the interaction of DipI with a protein complex that has been suggested to regulate cell wall synthesis during division, suggest that DipI may be part of the regulatory mechanism that controls constriction initiation.

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