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CbtA toxin of Escherichia coli inhibits cell division and cell elongation via direct and independent interactions with FtsZ and MreB. PLoS Genet 2017; 13:e1007007. [PMID: 28931012 PMCID: PMC5624674 DOI: 10.1371/journal.pgen.1007007] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 10/02/2017] [Accepted: 09/06/2017] [Indexed: 12/12/2022] Open
Abstract
The toxin components of toxin-antitoxin modules, found in bacterial plasmids, phages, and chromosomes, typically target a single macromolecule to interfere with an essential cellular process. An apparent exception is the chromosomally encoded toxin component of the E. coli CbtA/CbeA toxin-antitoxin module, which can inhibit both cell division and cell elongation. A small protein of only 124 amino acids, CbtA, was previously proposed to interact with both FtsZ, a tubulin homolog that is essential for cell division, and MreB, an actin homolog that is essential for cell elongation. However, whether or not the toxic effects of CbtA are due to direct interactions with these predicted targets is not known. Here, we genetically separate the effects of CbtA on cell elongation and cell division, showing that CbtA interacts directly and independently with FtsZ and MreB. Using complementary genetic approaches, we identify the functionally relevant target surfaces on FtsZ and MreB, revealing that in both cases, CbtA binds to surfaces involved in essential cytoskeletal filament architecture. We show further that each interaction contributes independently to CbtA-mediated toxicity and that disruption of both interactions is required to alleviate the observed toxicity. Although several other protein modulators are known to target FtsZ, the CbtA-interacting surface we identify represents a novel inhibitory target. Our findings establish CbtA as a dual function toxin that inhibits both cell division and cell elongation via direct and independent interactions with FtsZ and MreB. Bacterially encoded toxin-antitoxin systems, which consist of a small toxin protein that is co-produced with a neutralizing antitoxin, are a potential avenue for the identification of novel antibiotic targets. These toxins typically target essential cellular processes, causing growth arrest or cell death when unchecked by the antitoxin. Our study is focused on the CbtA toxin of E. coli, which was known to inhibit both bacterial cell division and also bacterial cell elongation (the process by which rod-shaped bacteria grow prior to cell division). We report that the effects of CbtA on cell division and cell elongation are genetically separable, and that they are due to direct and independent interactions with its targets FtsZ and MreB, essential cytoskeletal proteins that direct cell division and cell elongation, respectively. Our genetic analysis defines the functionally relevant target surfaces on FtsZ and MreB; in the case of FtsZ this surface represents a novel inhibitory target. As a dual-function toxin that independently targets two essential cytoskeletal elements, CbtA could guide the design of dual-function antibiotics whose ability to independently target more than one essential cellular process might impede the development of drug resistance, which is a growing public health threat.
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Dongamanti A, Aamate VK, Devulapally MG, Gundu S, Balabadra S, Manga V, Yogeeswari P, Sriram D, Balasubramanian S. Bis-spirochromanones as potent inhibitors of Mycobacterium tuberculosis: synthesis and biological evaluation. Mol Divers 2017; 21:999-1010. [PMID: 28840414 DOI: 10.1007/s11030-017-9779-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 08/02/2017] [Indexed: 11/30/2022]
Abstract
On the basis of reported antimycobacterial property of chroman-4-one pharmacophore, a series of chemically modified bis-spirochromanones were synthesized starting from 2-hydroxyacetophenone and 1,4-dioxaspiro[4.5] decan-8-one using a Kabbe condensation approach. The synthesized bis-spirochromanones were established based on their spectral data and X-ray crystal structure of 6e. All synthesized compounds were evaluated against Mycobacterium tuberculosis H37Rv (ATCC 27294) strain, finding that some products exhibited good antimycobacterial activity with minimum inhibitory concentration as low as [Formula: see text]. Docking studies were carried out to identify the binding interactions of compounds II, 6a and 6n with FtsZ. Compounds exhibiting good in vitro potency in the MTB MIC assay were further evaluated for toxicity using the HEK cell line.
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Affiliation(s)
- Ashok Dongamanti
- Green and Medicinal Chemistry Lab, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India.
| | - Vikas Kumar Aamate
- Green and Medicinal Chemistry Lab, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India
| | - Mohan Gandhi Devulapally
- Green and Medicinal Chemistry Lab, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India
| | - Srinivas Gundu
- Green and Medicinal Chemistry Lab, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India
| | - Saikrishna Balabadra
- Molecular Modeling and Medicinal Chemistry group, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India
| | - Vijjulatha Manga
- Molecular Modeling and Medicinal Chemistry group, Department of Chemistry, Osmania University, Hyderabad, Telangana State, 500 007, India
| | - Perumal Yogeeswari
- Department of Pharmacy, Birla Institute of Technology and Science - Pilani, Hyderabad Campus, Jawahar Nagar, Hyderabad, Telangana State, 500 078, India
| | - Dharmarajan Sriram
- Department of Pharmacy, Birla Institute of Technology and Science - Pilani, Hyderabad Campus, Jawahar Nagar, Hyderabad, Telangana State, 500 078, India
| | - Sridhar Balasubramanian
- X-ray Crystallography Division, CSIR-Indian Institute of Chemical Technology, Hyderabad, Telangana State, 500 007, India
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53
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van Teeseling MCF, de Pedro MA, Cava F. Determinants of Bacterial Morphology: From Fundamentals to Possibilities for Antimicrobial Targeting. Front Microbiol 2017; 8:1264. [PMID: 28740487 PMCID: PMC5502672 DOI: 10.3389/fmicb.2017.01264] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 06/23/2017] [Indexed: 12/11/2022] Open
Abstract
Bacterial morphology is extremely diverse. Specific shapes are the consequence of adaptive pressures optimizing bacterial fitness. Shape affects critical biological functions, including nutrient acquisition, motility, dispersion, stress resistance and interactions with other organisms. Although the characteristic shape of a bacterial species remains unchanged for vast numbers of generations, periodical variations occur throughout the cell (division) and life cycles, and these variations can be influenced by environmental conditions. Bacterial morphology is ultimately dictated by the net-like peptidoglycan (PG) sacculus. The species-specific shape of the PG sacculus at any time in the cell cycle is the product of multiple determinants. Some morphological determinants act as a cytoskeleton to guide biosynthetic complexes spatiotemporally, whereas others modify the PG sacculus after biosynthesis. Accumulating evidence supports critical roles of morphogenetic processes in bacteria-host interactions, including pathogenesis. Here, we review the molecular determinants underlying morphology, discuss the evidence linking bacterial morphology to niche adaptation and pathogenesis, and examine the potential of morphological determinants as antimicrobial targets.
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Affiliation(s)
- Muriel C F van Teeseling
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Miguel A de Pedro
- Centro de Biología Molecular "Severo Ochoa" - Consejo Superior de Investigaciones Científicas, Universidad Autónoma de MadridMadrid, Spain
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
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54
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Márquez IF, Mateos-Gil P, Shin JY, Lagos R, Monasterio O, Vélez M. Mutations on FtsZ lateral helix H3 that disrupt cell viability hamper reorganization of polymers on lipid surfaces. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017. [PMID: 28642045 DOI: 10.1016/j.bbamem.2017.06.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
FtsZ filaments localize at the middle of the bacterial cell and participate in the formation of a contractile ring responsible for cell division. Previous studies demonstrated that the highly conserved negative charge of glutamate 83 and the positive charge of arginine 85 located in the lateral helix H3 bend of Escherichia coli FtsZ are required for in vivo cell division. In order to understand how these lateral mutations impair the formation of a contractile ring,we extend previous in vitro characterization of these mutants in solution to study their behavior on lipid modified surfaces. We study their interaction with ZipAand look at their reorganization on the surface. We found that the dynamic bundling capacity of the mutant proteins is deficient, and this impairment increases the more the composition and spatial arrangement of the reconstituted system resembles the situation inside the cell: mutant proteins completely fail to reorganize to form higher order aggregates when bound to an E.coli lipid surface through oriented ZipA.We conclude that these surface lateral point mutations affect the dynamic reorganization of FtsZ filaments into bundles on the cell membrane, suggesting that this event is relevant for generating force and completing bacterial division.
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Affiliation(s)
- Ileana F Márquez
- Instituto de Catálisis y Petroleoquímica, c/Marie Curie 2, Cantoblanco, Madrid 28049, Spain
| | - Pablo Mateos-Gil
- Instituto de Catálisis y Petroleoquímica, c/Marie Curie 2, Cantoblanco, Madrid 28049, Spain
| | - Jae Yen Shin
- Departamento de Biología, Facultad de Ciencias, Casilla 653, Santiago 1, Chile
| | - Rosalba Lagos
- Departamento de Biología, Facultad de Ciencias, Casilla 653, Santiago 1, Chile
| | - Octavio Monasterio
- Departamento de Biología, Facultad de Ciencias, Casilla 653, Santiago 1, Chile
| | - Marisela Vélez
- Instituto de Catálisis y Petroleoquímica, c/Marie Curie 2, Cantoblanco, Madrid 28049, Spain.
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55
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Sun N, Lu YJ, Chan FY, Du RL, Zheng YY, Zhang K, So LY, Abagyan R, Zhuo C, Leung YC, Wong KY. A Thiazole Orange Derivative Targeting the Bacterial Protein FtsZ Shows Potent Antibacterial Activity. Front Microbiol 2017; 8:855. [PMID: 28553278 PMCID: PMC5426085 DOI: 10.3389/fmicb.2017.00855] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 04/27/2017] [Indexed: 01/02/2023] Open
Abstract
The prevalence of multidrug resistance among clinically significant bacteria calls for the urgent development of new antibiotics with novel mechanisms of action. In this study, a new small molecule exhibiting excellent inhibition of bacterial cell division with potent antibacterial activity was discovered through cell-based screening. The compound exhibits a broad spectrum of bactericidal activity, including the methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and NDM-1 Escherichia coli. The in vitro and in vivo results suggested that this compound disrupts the dynamic assembly of FtsZ protein and Z-ring formation through stimulating FtsZ polymerization. Moreover, this compound exhibits no activity on mammalian tubulin polymerization and shows low cytotoxicity on mammalian cells. Taken together, these findings could provide a new chemotype for development of antibacterials with FtsZ as the target.
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Affiliation(s)
- Ning Sun
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
| | - Yu-Jing Lu
- Institute of Natural Medicine and Green Chemistry, School of Chemical Engineering and Light Industry, Guangdong University of TechnologyGuangzhou, China
| | - Fung-Yi Chan
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
| | - Ruo-Lan Du
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
| | - Yuan-Yuan Zheng
- Institute of Natural Medicine and Green Chemistry, School of Chemical Engineering and Light Industry, Guangdong University of TechnologyGuangzhou, China
| | - Kun Zhang
- Institute of Natural Medicine and Green Chemistry, School of Chemical Engineering and Light Industry, Guangdong University of TechnologyGuangzhou, China
| | - Lok-Yan So
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
| | - Ruben Abagyan
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La JollaCA, USA
| | - Chao Zhuo
- State Key Laboratory of Respiratory Diseases, the First Affiliated Hospital of Guangzhou Medical UniversityGuangzhou, China
| | - Yun-Chung Leung
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
| | - Kwok-Yin Wong
- Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences, The Hong Kong Polytechnic UniversityHong Kong, Hong Kong
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56
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Wagstaff JM, Tsim M, Oliva MA, García-Sanchez A, Kureisaite-Ciziene D, Andreu JM, Löwe J. A Polymerization-Associated Structural Switch in FtsZ That Enables Treadmilling of Model Filaments. mBio 2017; 8:e00254-17. [PMID: 28465423 PMCID: PMC5414002 DOI: 10.1128/mbio.00254-17] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 04/13/2017] [Indexed: 02/07/2023] Open
Abstract
Bacterial cell division in many organisms involves a constricting cytokinetic ring that is orchestrated by the tubulin-like protein FtsZ. FtsZ forms dynamic filaments close to the membrane at the site of division that have recently been shown to treadmill around the division ring, guiding septal wall synthesis. Here, using X-ray crystallography of Staphylococcus aureus FtsZ (SaFtsZ), we reveal how an FtsZ can adopt two functionally distinct conformations, open and closed. The open form is found in SaFtsZ filaments formed in crystals and also in soluble filaments of Escherichia coli FtsZ as deduced by electron cryomicroscopy. The closed form is found within several crystal forms of two nonpolymerizing SaFtsZ mutants and corresponds to many previous FtsZ structures from other organisms. We argue that FtsZ's conformational switch is polymerization-associated, driven by the formation of the longitudinal intersubunit interfaces along the filament. We show that such a switch provides explanations for both how treadmilling may occur within a single-stranded filament and why filament assembly is cooperative.IMPORTANCE The FtsZ protein is a key molecule during bacterial cell division. FtsZ forms filaments that organize cell membrane constriction, as well as remodeling of the cell wall, to divide cells. FtsZ functions through nucleotide-driven filament dynamics that are poorly understood at the molecular level. In particular, mechanisms for cooperative assembly (nonlinear dependency on concentration) and treadmilling (preferential growth at one filament end and loss at the other) have remained elusive. Here, we show that most likely all FtsZ proteins have two distinct conformations, a "closed" form in monomeric FtsZ and an "open" form in filaments. The conformational switch that occurs upon polymerization explains cooperativity and, in concert with polymerization-dependent nucleotide hydrolysis, efficient treadmilling of FtsZ polymers.
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Affiliation(s)
| | - Matthew Tsim
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - María A Oliva
- Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | | | | | | | - Jan Löwe
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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57
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Fujita J, Harada R, Maeda Y, Saito Y, Mizohata E, Inoue T, Shigeta Y, Matsumura H. Identification of the key interactions in structural transition pathway of FtsZ from Staphylococcus aureus. J Struct Biol 2017; 198:65-73. [PMID: 28456664 DOI: 10.1016/j.jsb.2017.04.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 04/18/2017] [Accepted: 04/25/2017] [Indexed: 10/19/2022]
Abstract
The tubulin-homolog protein FtsZ is essential for bacterial cell division. FtsZ polymerizes to form protofilaments that assemble into a contractile ring-shaped structure in the presence of GTP. Recent studies showed that FtsZ treadmilling coupled with the GTPase activity drives cell wall synthesis and bacterial cell division. The treadmilling caused by assembly and disassembly of FtsZ links to a conformational change of the monomer from a tense (T) to a relaxed (R) state, but considerable controversy still remains concerning the mechanism. In this study, we report crystal structures of FtsZ from Staphylococcus aureus corresponding to the T and R state conformations in the same crystal, indicating the structural equilibrium of the two state. The two structures identified a key residue Arg29, whose importance was also confirmed by our modified MD simulations. Crystal structures of the R29A mutant showed T and R state-like conformations with slight but important structural changes compared to those of wild-type. Collectively, these data provide new insights for understanding how intramolecular interactions are related to the structural transition of FtsZ.
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Affiliation(s)
- Junso Fujita
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ryuhei Harada
- Graduate School of Pure and Applied Sciences/Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
| | - Yoko Maeda
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yuki Saito
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Eiichi Mizohata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tsuyoshi Inoue
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yasuteru Shigeta
- Graduate School of Pure and Applied Sciences/Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
| | - Hiroyoshi Matsumura
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
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58
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Gardner KAJA, Osawa M, Erickson HP. Whole genome re-sequencing to identify suppressor mutations of mutant and foreign Escherichia coli FtsZ. PLoS One 2017; 12:e0176643. [PMID: 28445510 PMCID: PMC5405962 DOI: 10.1371/journal.pone.0176643] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 04/13/2017] [Indexed: 01/07/2023] Open
Abstract
FtsZ is an essential protein for bacterial cell division, where it forms the cytoskeletal scaffold and may generate the constriction force. We have found previously that some mutant and foreign FtsZ that do not complement an ftsZ null can function for cell division in E. coli upon acquisition of a suppressor mutation somewhere in the genome. We have now identified, via whole genome re-sequencing, single nucleotide polymorphisms in 11 different suppressor strains. Most of the mutations are in genes of various metabolic pathways, which may modulate cell division indirectly. Mutations in three genes, ispA, accD and nlpI, may be more directly involved in cell division. In addition to the genomic suppressor mutations, we identified intragenic suppressors of three FtsZ point mutants (R174A, E250K and L272V).
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Affiliation(s)
- Kiani A. J. Arkus Gardner
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Masaki Osawa
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Harold P. Erickson
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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59
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Ojima I, Awasthi D, Wei L, Haranahalli K. Strategic incorporation of fluorine in the drug discovery of new-generation antitubercular agents targeting bacterial cell division protein FtsZ. J Fluor Chem 2017; 196:44-56. [PMID: 28555087 PMCID: PMC5445929 DOI: 10.1016/j.jfluchem.2016.07.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
This article presents an account of our research on the discovery and development of new-generation fluorine-containing antibacterial agents against drug-resistant tuberculosis, targeting FtsZ. FtsZ is an essential protein for bacterial cell division and a highly promising therapeutic target for antibacterial drug discovery. Through design, synthesis and semi-HTP screening of libraries of novel benzimidazoles, followed by SAR studies, we identified highly potent lead compounds. However, these lead compounds were found to lack sufficient metabolic and plasma stabilities. Accordingly, we have performed extensive study on the strategic incorporation of fluorine into lead compounds to improve pharmacological properties. This study has led to the development of highly efficacious fluorine-containing benzimidazoles as potential drug candidates. We have also performed computational docking analysis of these novel FtsZ inhibitors to identify their putative binding site. Based on the structural data and docking analysis, a plausible mode-of-action for this novel class of FtsZ inhibitors is proposed.
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Affiliation(s)
- Iwao Ojima
- Department of Chemistry, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
- Institute of Chemical Biology & Drug Discovery, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
| | - Divya Awasthi
- Department of Chemistry, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
- Institute of Chemical Biology & Drug Discovery, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
| | - Longfei Wei
- Department of Chemistry, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
| | - Krupanandan Haranahalli
- Department of Chemistry, Stony Brook University—State University of New York, Stony Brook, NY, 11794-3400, USA
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60
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A New Essential Cell Division Protein in Caulobacter crescentus. J Bacteriol 2017; 199:JB.00811-16. [PMID: 28167520 DOI: 10.1128/jb.00811-16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 01/31/2017] [Indexed: 11/20/2022] Open
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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61
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Matsui T, Lallo S, Nisa K, Morita H. Filamenting temperature-sensitive mutant Z inhibitors from Glycyrrhiza glabra and their inhibitory mode of action. Bioorg Med Chem Lett 2017; 27:1420-1424. [DOI: 10.1016/j.bmcl.2017.01.095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 01/26/2017] [Accepted: 01/30/2017] [Indexed: 10/20/2022]
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62
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Cytoskeletal Proteins in Caulobacter crescentus: Spatial Orchestrators of Cell Cycle Progression, Development, and Cell Shape. Subcell Biochem 2017; 84:103-137. [PMID: 28500524 DOI: 10.1007/978-3-319-53047-5_4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Caulobacter crescentus, an aquatic Gram-negative α-proteobacterium, is dimorphic, as a result of asymmetric cell divisions that give rise to a free-swimming swarmer daughter cell and a stationary stalked daughter. Cell polarity of vibrioid C. crescentus cells is marked by the presence of a stalk at one end in the stationary form and a polar flagellum in the motile form. Progression through the cell cycle and execution of the associated morphogenetic events are tightly controlled through regulation of the abundance and activity of key proteins. In synergy with the regulation of protein abundance or activity, cytoskeletal elements are key contributors to cell cycle progression through spatial regulation of developmental processes. These include: polarity establishment and maintenance, DNA segregation, cytokinesis, and cell elongation. Cytoskeletal proteins in C. crescentus are additionally required to maintain its rod shape, curvature, and pole morphology. In this chapter, we explore the mechanisms through which cytoskeletal proteins in C. crescentus orchestrate developmental processes by acting as scaffolds for protein recruitment, generating force, and/or restricting or directing the motion of molecular machines. We discuss each cytoskeletal element in turn, beginning with those important for organization of molecules at the cell poles and chromosome segregation, then cytokinesis, and finally cell shape.
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63
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Loose M, Zieske K, Schwille P. Reconstitution of Protein Dynamics Involved in Bacterial Cell Division. Subcell Biochem 2017; 84:419-444. [PMID: 28500535 DOI: 10.1007/978-3-319-53047-5_15] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Even simple cells like bacteria have precisely regulated cellular anatomies, which allow them to grow, divide and to respond to internal or external cues with high fidelity. How spatial and temporal intracellular organization in prokaryotic cells is achieved and maintained on the basis of locally interacting proteins still remains largely a mystery. Bulk biochemical assays with purified components and in vivo experiments help us to approach key cellular processes from two opposite ends, in terms of minimal and maximal complexity. However, to understand how cellular phenomena emerge, that are more than the sum of their parts, we have to assemble cellular subsystems step by step from the bottom up. Here, we review recent in vitro reconstitution experiments with proteins of the bacterial cell division machinery and illustrate how they help to shed light on fundamental cellular mechanisms that constitute spatiotemporal order and regulate cell division.
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Affiliation(s)
- Martin Loose
- Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria.
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64
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Abstract
FtsZ assembles in vitro into protofilaments (pfs) that are one subunit thick and ~50 subunits long. In vivo these pfs assemble further into the Z ring, which, along with accessory division proteins, constricts to divide the cell. We have reconstituted Z rings in liposomes in vitro, using pure FtsZ that was modified with a membrane targeting sequence to directly bind the membrane. This FtsZ-mts assembled Z rings and constricted the liposomes without any accessory proteins. We proposed that the force for constriction was generated by a conformational change from straight to curved pfs. Evidence supporting this mechanism came from switching the membrane tether to the opposite side of the pf. These switched-tether pfs assembled "inside-out" Z rings, and squeezed the liposomes from the outside, as expected for the bending model. We propose three steps for the full process of cytokinesis: (a) pf bending generates a constriction force on the inner membrane, but the rigid peptidoglycan wall initially prevents any invagination; (b) downstream proteins associate to the Z ring and remodel the peptidoglycan, permitting it to follow the constricting FtsZ to a diameter of ~250 nm; the final steps of closure of the septum and membrane fusion are achieved by excess membrane synthesis and membrane fluctuations.
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Affiliation(s)
- Harold P Erickson
- Department of Cell Biology, Duke University, Durham, NC, 27710, USA.
| | - Masaki Osawa
- Department of Cell Biology, Duke University, Durham, NC, 27710, USA
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65
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Probing for Binding Regions of the FtsZ Protein Surface through Site-Directed Insertions: Discovery of Fully Functional FtsZ-Fluorescent Proteins. J Bacteriol 2016; 199:JB.00553-16. [PMID: 27795325 DOI: 10.1128/jb.00553-16] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 10/04/2016] [Indexed: 11/20/2022] Open
Abstract
FtsZ, a bacterial tubulin homologue, is a cytoskeletal protein that assembles into protofilaments that are one subunit thick. These protofilaments assemble further to form a "Z ring" at the center of prokaryotic cells. The Z ring generates a constriction force on the inner membrane and also serves as a scaffold to recruit cell wall remodeling proteins for complete cell division in vivo One model of the Z ring proposes that protofilaments associate via lateral bonds to form ribbons; however, lateral bonds are still only hypothetical. To explore potential lateral bonding sites, we probed the surface of Escherichia coli FtsZ by inserting either small peptides or whole fluorescent proteins (FPs). Among the four lateral surfaces on FtsZ protofilaments, we obtained inserts on the front and back surfaces that were functional for cell division. We concluded that these faces are not sites of essential interactions. Inserts at two sites, G124 and R174, located on the left and right surfaces, completely blocked function, and these sites were identified as possible sites for essential lateral interactions. However, the insert at R174 did not interfere with association of protofilaments into sheets and bundles in vitro Another goal was to find a location within FtsZ that supported insertion of FP reporter proteins while allowing the FtsZ-FPs to function as the sole source of FtsZ. We discovered one internal site, G55-Q56, where several different FPs could be inserted without impairing function. These FtsZ-FPs may provide advances for imaging Z-ring structure by superresolution techniques. IMPORTANCE One model for the Z-ring structure proposes that protofilaments are assembled into ribbons by lateral bonds between FtsZ subunits. Our study excluded the involvement of the front and back faces of the protofilament in essential interactions in vivo but pointed to two potential lateral bond sites, on the right and left sides. We also identified an FtsZ loop where various fluorescent proteins could be inserted without blocking function; these FtsZ-FPs functioned as the sole source of FtsZ. This advance provides improved tools for all fluorescence imaging of the Z ring and may be especially important for superresolution imaging.
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66
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Coltharp C, Xiao J. Beyond force generation: Why is a dynamic ring of FtsZ polymers essential for bacterial cytokinesis? Bioessays 2016; 39:1-11. [PMID: 28004447 DOI: 10.1002/bies.201600179] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We propose that the essential function of the most highly conserved protein in bacterial cytokinesis, FtsZ, is not to generate a mechanical force to drive cell division. Rather, we suggest that FtsZ acts as a signal-processing hub to coordinate cell wall synthesis at the division septum with a diverse array of cellular processes, ensuring that the cell divides smoothly at the correct time and place, and with the correct septum morphology. Here, we explore how the polymerization properties of FtsZ, which have been widely attributed to force generation, can also be advantageous in this signal processing role. We suggest mechanisms by which FtsZ senses and integrates both mechanical and biochemical signals, and conclude by proposing experiments to investigate how FtsZ contributes to the remarkable spatial and temporal precision of bacterial cytokinesis.
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Affiliation(s)
- Carla Coltharp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA
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67
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Exploring the possible binding mode of trisubstituted benzimidazoles analogues in silico for novel drug designtargeting Mtb FtsZ. Med Chem Res 2016. [DOI: 10.1007/s00044-016-1734-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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68
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Bohuszewicz O, Liu J, Low HH. Membrane remodelling in bacteria. J Struct Biol 2016; 196:3-14. [PMID: 27265614 PMCID: PMC6168058 DOI: 10.1016/j.jsb.2016.05.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 05/20/2016] [Accepted: 05/26/2016] [Indexed: 01/10/2023]
Abstract
In bacteria the ability to remodel membrane underpins basic cell processes such as growth, and more sophisticated adaptations like inter-cell crosstalk, organelle specialisation, and pathogenesis. Here, selected examples of membrane remodelling in bacteria are presented and the diverse mechanisms for inducing membrane fission, fusion, and curvature discussed. Compared to eukaryotes, relatively few curvature-inducing proteins have been characterised so far. Whilst it is likely that many such proteins remain to be discovered, it also reflects the importance of alternative membrane remodelling strategies in bacteria where passive mechanisms for generating curvature are utilised.
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Affiliation(s)
- Olga Bohuszewicz
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK
| | - Jiwei Liu
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK
| | - Harry H Low
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK.
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69
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Lyu Z, Coltharp C, Yang X, Xiao J. Influence of FtsZ GTPase activity and concentration on nanoscale Z-ring structure in vivo revealed by three-dimensional Superresolution imaging. Biopolymers 2016; 105:725-34. [PMID: 27310678 PMCID: PMC4958570 DOI: 10.1002/bip.22895] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 12/18/2022]
Abstract
FtsZ is an essential bacterial cytoskeletal protein that assembles into a ring-like structure (Z-ring) at midcell to carry out cytokinesis. In vitro, FtsZ exhibits polymorphism in polymerizing into different forms of filaments based on its GTPase activity, concentration, and buffer condition. In vivo, the Z-ring appeared to be punctate and heterogeneously organized, although continuous, homogenous Z-ring structures have also been observed. Understanding how the Z-ring is organized in vivo is important because it provides a structural basis for the functional role of the Z-ring in cytokinesis. Here, we assess the effects of both GTPase activity and FtsZ concentration on the organization of the Z-ring in vivo using three-dimensional (3D) superresolution microscopy. We found that the Z-ring became more homogenous when assembled in the presence of a GTPase-deficient mutant, and upon overexpression of either wt or mutant FtsZ. These results suggest that the in vivo organization of the Z-ring is largely dependent on the intrinsic polymerization properties of FtsZ, which are significantly influenced by the GTPase activity and concentration of FtsZ. Our work provides a unifying theme to reconcile previous observations of different Z-ring structures, and supports a model in which the wt Z-ring comprises loosely associated, heterogeneously distributed FtsZ clusters. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 725-734, 2016.
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Affiliation(s)
- Zhixin Lyu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD
| | - Carla Coltharp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD
| | - Xinxing Yang
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD
| | - Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD
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70
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Xiao J, Goley ED. Redefining the roles of the FtsZ-ring in bacterial cytokinesis. Curr Opin Microbiol 2016; 34:90-96. [PMID: 27620716 DOI: 10.1016/j.mib.2016.08.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 08/25/2016] [Accepted: 08/25/2016] [Indexed: 02/05/2023]
Abstract
In most bacteria, cell division relies on the functions of an essential protein, FtsZ. FtsZ polymerizes at the future division site to form a ring-like structure, termed the Z-ring, that serves as a scaffold to recruit all other division proteins, and possibly generates force to constrict the cell. The scaffolding function of the Z-ring is well established, but the force generating function has recently been called into question. Additionally, new findings have demonstrated that the Z-ring is more directly linked to cell wall metabolism than simply recruiting enzymes to the division site. Here we review these advances and suggest that rather than generating a rate-limiting constrictive force, the Z-ring's function may be redefined as an orchestrator of septum synthesis.
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Affiliation(s)
- Jie Xiao
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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71
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FtsZ does not initiate membrane constriction at the onset of division. Sci Rep 2016; 6:33138. [PMID: 27609565 PMCID: PMC5016829 DOI: 10.1038/srep33138] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/22/2016] [Indexed: 01/01/2023] Open
Abstract
The source of constriction required for division of a bacterial cell remains enigmatic. FtsZ is widely believed to be a key player, because in vitro experiments indicate that it can deform liposomes when membrane tethered. However in vivo evidence for such a role has remained elusive as it has been challenging to distinguish the contribution of FtsZ from that of peptidoglycan-ingrowth. To differentiate between these two possibilities we studied the early stages of division in Escherichia coli, when FtsZ is present at the division site but peptidoglycan synthesizing enzymes such as FtsI and FtsN are not. Our approach was to use correlative cryo-fluorescence and cryo-electron microscopy (cryo-CLEM) to monitor the localization of fluorescently labeled FtsZ, FtsI or FtsN correlated with the septal ultra-structural geometry in the same cell. We noted that the presence of FtsZ at the division septum is not sufficient to deform membranes. This observation suggests that, although FtsZ can provide a constrictive force, the force is not substantial at the onset of division. Conversely, the presence of FtsN always correlated with membrane invagination, indicating that allosteric activation of peptidoglycan ingrowth is the trigger for constriction of the cell envelope during cell division in E. coli.
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72
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Abstract
A mechanistic understanding of the determination and maintenance of the simplest bacterial cell shape, a sphere, remains elusive compared with that of more complex shapes. Cocci seem to lack a dedicated elongation machinery, and a spherical shape has been considered an evolutionary dead-end morphology, as a transition from a spherical to a rod-like shape has never been observed in bacteria. Here we show that a Staphylococcus aureus mutant (M5) expressing the ftsZG193D allele exhibits elongated cells. Molecular dynamics simulations and in vitro studies indicate that FtsZG193D filaments are more twisted and shorter than wild-type filaments. In vivo, M5 cell wall deposition is initiated asymmetrically, only on one side of the cell, and progresses into a helical pattern rather than into a constricting ring as in wild-type cells. This helical pattern of wall insertion leads to elongation, as in rod-shaped cells. Thus, structural flexibility of FtsZ filaments can result in an FtsZ-dependent mechanism for generating elongated cells from cocci. The mechanisms by which bacteria generate and maintain even the simplest cell shape remain an elusive but fundamental question in microbiology. In the absence of examples of coccus-to-rod transitions, the spherical shape has been suggested to be an evolutionary dead end in morphogenesis. We describe the first observation of the generation of elongated cells from truly spherical cocci, occurring in a Staphylococcus aureus mutant containing a single point mutation in its genome, in the gene encoding the bacterial tubulin homologue FtsZ. We demonstrate that FtsZ-dependent cell elongation is possible, even in the absence of dedicated elongation machinery.
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73
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Housman M, Milam SL, Moore DA, Osawa M, Erickson HP. FtsZ Protofilament Curvature Is the Opposite of Tubulin Rings. Biochemistry 2016; 55:4085-91. [PMID: 27368355 DOI: 10.1021/acs.biochem.6b00479] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
FtsZ protofilaments (pfs) form the bacterial cytokinetic Z ring. Previous work suggested that a conformational change from straight to curved pfs generated the constriction force. In the simplest model, the C-terminal membrane tether is on the outside of the curved pf, facing the membrane. Tubulin, a homologue of FtsZ, also forms pfs with a curved conformation. However, it is well-established that tubulin rings have the C terminus on the inside of the ring. Could FtsZ and tubulin rings have the opposite curvature? In this study, we explored the FtsZ curvature direction by fusing large protein tags to the FtsZ termini. Thin section electron microscopy showed that the C-terminal tag was on the outside, consistent with the bending pf model. This has interesting implications for the evolution of tubulin. Tubulin likely began with the curvature of FtsZ, but evolution managed to reverse direction to produce outward-curving rings, which are useful for pulling chromosomes.
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Affiliation(s)
- Max Housman
- Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Sara L Milam
- Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Desmond A Moore
- Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Masaki Osawa
- Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Harold P Erickson
- Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States
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74
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Baranova N, Loose M. Single-molecule measurements to study polymerization dynamics of FtsZ-FtsA copolymers. Methods Cell Biol 2016; 137:355-370. [PMID: 28065316 DOI: 10.1016/bs.mcb.2016.03.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bacterial cytokinesis is commonly initiated by the Z-ring, a dynamic cytoskeletal structure that assembles at the site of division. Its primary component is FtsZ, a tubulin-like GTPase, that like its eukaryotic relative forms protein filaments in the presence of GTP. Since the discovery of the Z-ring 25years ago, various models for the role of FtsZ have been suggested. However, important information about the architecture and dynamics of FtsZ filaments during cytokinesis is still missing. One reason for this lack of knowledge has been the small size of bacteria, which has made it difficult to resolve the orientation and dynamics of individual FtsZ filaments in the Z-ring. While superresolution microscopy experiments have helped to gain more information about the organization of the Z-ring in the dividing cell, they were not yet able to elucidate a mechanism of how FtsZ filaments reorganize during assembly and disassembly of the Z-ring. In this chapter, we explain how to use an in vitro reconstitution approach to investigate the self-organization of FtsZ filaments recruited to a biomimetic lipid bilayer by its membrane anchor FtsA. We show how to perform single-molecule experiments to study the behavior of individual FtsZ monomers during the constant reorganization of the FtsZ-FtsA filament network. We describe how to analyze the dynamics of single molecules and explain why this information can help to shed light onto possible mechanism of Z-ring constriction. We believe that similar experimental approaches will be useful to study the mechanism of membrane-based polymerization of other cytoskeletal systems, not only from prokaryotic but also eukaryotic origin.
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Affiliation(s)
- N Baranova
- Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - M Loose
- Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria
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75
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Busiek KK, Margolin W. Bacterial actin and tubulin homologs in cell growth and division. Curr Biol 2016; 25:R243-R254. [PMID: 25784047 DOI: 10.1016/j.cub.2015.01.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In contrast to the elaborate cytoskeletal machines harbored by eukaryotic cells, such as mitotic spindles, cytoskeletal structures detectable by typical negative stain electron microscopy are generally absent from bacterial cells. As a result, for decades it was thought that bacteria lacked cytoskeletal machines. Revolutions in genomics and fluorescence microscopy have confirmed the existence not only of smaller-scale cytoskeletal structures in bacteria, but also of widespread functional homologs of eukaryotic cytoskeletal proteins. The presence of actin, tubulin, and intermediate filament homologs in these relatively simple cells suggests that primitive cytoskeletons first arose in bacteria. In bacteria such as Escherichia coli, homologs of tubulin and actin directly interact with each other and are crucial for coordinating cell growth and division. The function and direct interactions between these proteins will be the focus of this review.
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Affiliation(s)
- Kimberly K Busiek
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX 77030, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX 77030, USA.
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76
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Structures of the nucleoid occlusion protein SlmA bound to DNA and the C-terminal domain of the cytoskeletal protein FtsZ. Proc Natl Acad Sci U S A 2016; 113:4988-93. [PMID: 27091999 DOI: 10.1073/pnas.1602327113] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cell division in most prokaryotes is mediated by FtsZ, which polymerizes to create the cytokinetic Z ring. Multiple FtsZ-binding proteins regulate FtsZ polymerization to ensure the proper spatiotemporal formation of the Z ring at the division site. The DNA-binding protein SlmA binds to FtsZ and prevents Z-ring formation through the nucleoid in a process called "nucleoid occlusion" (NO). As do most FtsZ-accessory proteins, SlmA interacts with the conserved C-terminal domain (CTD) that is connected to the FtsZ core by a long, flexible linker. However, SlmA is distinct from other regulatory factors in that it must be DNA-bound to interact with the FtsZ CTD. Few structures of FtsZ regulator-CTD complexes are available, but all reveal the CTD bound as a helix. To deduce the molecular basis for the unique SlmA-DNA-FtsZ CTD regulatory interaction and provide insight into FtsZ-regulator protein complex formation, we determined structures of Escherichia coli, Vibrio cholera, and Klebsiella pneumonia SlmA-DNA-FtsZ CTD ternary complexes. Strikingly, the FtsZ CTD does not interact with SlmA as a helix but binds as an extended conformation in a narrow, surface-exposed pocket formed only in the DNA-bound state of SlmA and located at the junction between the DNA-binding and C-terminal dimer domains. Binding studies are consistent with the structure and underscore key interactions in complex formation. Combined, these data reveal the molecular basis for the SlmA-DNA-FtsZ interaction with implications for SlmA's NO function and underscore the ability of the FtsZ CTD to adopt a wide range of conformations, explaining its ability to bind diverse regulatory proteins.
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77
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Haeusser DP, Margolin W. Splitsville: structural and functional insights into the dynamic bacterial Z ring. Nat Rev Microbiol 2016; 14:305-19. [PMID: 27040757 DOI: 10.1038/nrmicro.2016.26] [Citation(s) in RCA: 216] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacteria must divide to increase in number and colonize their niche. Binary fission is the most widespread means of bacterial cell division, but even this relatively simple mechanism has many variations on a theme. In most bacteria, the tubulin homologue FtsZ assembles into a ring structure, termed the Z ring, at the site of cytokinesis and recruits additional proteins to form a large protein machine - the divisome - that spans the membrane. In this Review, we discuss current insights into the regulation of the assembly of the Z ring and how the divisome drives membrane invagination and septal cell wall growth while flexibly responding to various cellular inputs.
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Affiliation(s)
- Daniel P Haeusser
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin Street, Houston, Texas 77030, USA.,Biology Department, Canisius College, 2001 Main Street, Buffalo, New York 14208, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin Street, Houston, Texas 77030, USA
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78
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Nishida Y, Takeuchi H, Morimoto N, Umeda A, Kadota Y, Kira M, Okazaki A, Matsumura Y, Sugiura T. Intrinsic characteristics of Min proteins on the cell division of Helicobacter pylori. FEMS Microbiol Lett 2016; 363:fnw025. [PMID: 26862143 DOI: 10.1093/femsle/fnw025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2016] [Indexed: 01/24/2023] Open
Abstract
Helicobacter pylori divides in the human stomach resulting in persistent infections and causing various disorders. Bacterial cell division is precisely coordinated by many molecules, including FtsZ and Min proteins. However, the role of Min proteins in H. pylori division is poorly understood. We investigated the functional characteristics of Min proteins in wild-type HPK5 and five HPK5-derivative mutants using morphological and genetic approaches. All mutants showed a filamentous shape. However, the bacterial cell growth and viability of three single-gene mutants (minC, minD, minE) were similar to that of the wild-type. The coccoid form number was lowest in the minE-disruptant, indicating that MinE contributes to the coccoid form conversion during the stationary phase. Immunofluorescence microscopic observations showed that FtsZ was dispersedly distributed throughout the bacterial cell irrespective of nucleoid position in only minD-disruptants, indicating that MinD is involved in the nucleoid occlusion system. A chase assay demonstrated that MinC loss suppressed FtsZ-degradation, indicating that FtsZ degrades in a MinC-dependent manner. Molecular interactions between FtsZ and Min proteins were confirmed by immunoprecipitation (IP)-western blotting (WB), suggesting the functional cooperation of these molecules during bacterial cell division. This study describes the intrinsic characteristics of Min proteins and provides new insights into H. pylori cell division.
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Affiliation(s)
- Yoshie Nishida
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Hiroaki Takeuchi
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Norihito Morimoto
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Akiko Umeda
- Department of Clinical Laboratory Medicine, Yamaguchi University, 1-1-1 MinamiKogushi, Ube-city, Yamaguchi 755-8505, Japan
| | - Yoshu Kadota
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Mizuki Kira
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Ami Okazaki
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Yoshihisa Matsumura
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
| | - Tetsuro Sugiura
- Department of Clinical Laboratory Medicine, Kochi Medical School, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan
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79
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Abstract
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.
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80
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Hepler PK. The Cytoskeleton and Its Regulation by Calcium and Protons. PLANT PHYSIOLOGY 2016; 170:3-22. [PMID: 26722019 PMCID: PMC4704593 DOI: 10.1104/pp.15.01506] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 11/28/2015] [Indexed: 05/18/2023]
Abstract
Calcium and protons exert control over the formation and activity of the cytoskeleton, usually by modulating an associated motor protein or one that affects the structural organization of the polymer.
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Affiliation(s)
- Peter K Hepler
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003
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81
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Adams DW, Wu LJ, Errington J. A benzamide-dependent ftsZ mutant reveals residues crucial for Z-ring assembly. Mol Microbiol 2015; 99:1028-42. [PMID: 26601800 PMCID: PMC4832351 DOI: 10.1111/mmi.13286] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2015] [Indexed: 12/14/2022]
Abstract
In almost all bacteria, cell division is co-ordinated by the essential tubulin homologue FtsZ and represents an attractive but as yet unexploited target for new antibiotics. The benzamides, e.g. PC190723, are potent FtsZ inhibitors that have the potential to yield an important new class of antibiotic. However, the evolution of resistance poses a challenge to their development. Here we show that a collection of PC190723-resistant and -dependent strains of Staphylococcus aureus exhibit severe growth and morphological defects, questioning whether these ftsZ mutations would be clinically relevant. Importantly, we show that the most commonly isolated substitution remains sensitive to the simplest benzamide 3-MBA and likely works by occluding compound binding. Extending this analysis to Bacillus subtilis, we isolated a novel benzamide-dependent strain that divides using unusual helical division events. The ftsZ mutation responsible encodes the substitution of a highly conserved residue, which lies outside the benzamide-binding site and forms part of an interface between the N- and C-terminal domains that we show is necessary for normal FtsZ function. Together with an intragenic suppressor mutation that mimics benzamide binding, the results provide genetic evidence that benzamides restrict conformational changes in FtsZ and also highlights their utility as tools to probe bacterial division.
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Affiliation(s)
- David William Adams
- Centre for Bacterial Cell Biology, Baddiley-Clark Building, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
| | - Ling Juan Wu
- Centre for Bacterial Cell Biology, Baddiley-Clark Building, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
| | - Jeff Errington
- Centre for Bacterial Cell Biology, Baddiley-Clark Building, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
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82
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Abstract
Traditionally eukaryotes exclusive cytoskeleton has been found in bacteria and other prokaryotes. FtsZ, MreB and CreS are bacterial counterpart of eukaryotic tubulin, actin filaments and intermediate filaments, respectively. FtsZ can assemble to a Z-ring at the cell division site, regulate bacterial cell division; MreB can form helical structure, and involve in maintaining cell shape, regulating chromosome segregation; CreS, found in Caulobacter crescentus (C. crescentus), can form curve or helical filaments in intracellular membrane. CreS is crucial for cell morphology maintenance. There are also some prokaryotic unique cytoskeleton components playing crucial roles in cell division, chromosome segregation and cell morphology. The cytoskeleton components of Mycobacterium tuberculosis (M. tuberculosis), together with their dynamics during exposure to antibiotics are summarized in this article to provide insights into the unique organization of this formidable pathogen and druggable targets for new antibiotics.
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Affiliation(s)
- Huan Wang
- a Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Ministry of Education Eco-Environment of the Three Gorges Reservoir Region, School of Life Sciences, Southwest University , Chongqing , China
| | - Longxiang Xie
- a Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Ministry of Education Eco-Environment of the Three Gorges Reservoir Region, School of Life Sciences, Southwest University , Chongqing , China
| | - Hongping Luo
- a Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Ministry of Education Eco-Environment of the Three Gorges Reservoir Region, School of Life Sciences, Southwest University , Chongqing , China
| | - Jianping Xie
- a Institute of Modern Biopharmaceuticals, State Key Laboratory Breeding Base of Eco-Environment and Bio-Resource of the Three Gorges Area, Key Laboratory of Ministry of Education Eco-Environment of the Three Gorges Reservoir Region, School of Life Sciences, Southwest University , Chongqing , China
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83
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Remodeling of the Z-Ring Nanostructure during the Streptococcus pneumoniae Cell Cycle Revealed by Photoactivated Localization Microscopy. mBio 2015; 6:mBio.01108-15. [PMID: 26286692 PMCID: PMC4542196 DOI: 10.1128/mbio.01108-15] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ovococci form a morphological group that includes several human pathogens (enterococci and streptococci). Their shape results from two modes of cell wall insertion, one allowing division and one allowing elongation. Both cell wall synthesis modes rely on a single cytoskeletal protein, FtsZ. Despite the central role of FtsZ in ovococci, a detailed view of the in vivo nanostructure of ovococcal Z-rings has been lacking thus far, limiting our understanding of their assembly and architecture. We have developed the use of photoactivated localization microscopy (PALM) in the ovococcus human pathogen Streptococcus pneumoniae by engineering spDendra2, a photoconvertible fluorescent protein optimized for this bacterium. Labeling of endogenously expressed FtsZ with spDendra2 revealed the remodeling of the Z-ring’s morphology during the division cycle at the nanoscale level. We show that changes in the ring’s axial thickness and in the clustering propensity of FtsZ correlate with the advancement of the cell cycle. In addition, we observe double-ring substructures suggestive of short-lived intermediates that may form upon initiation of septal cell wall synthesis. These data are integrated into a model describing the architecture and the remodeling of the Z-ring during the cell cycle of ovococci. The Gram-positive human pathogen S. pneumoniae is responsible for 1.6 million deaths per year worldwide and is increasingly resistant to various antibiotics. FtsZ is a cytoskeletal protein polymerizing at midcell into a ring-like structure called the Z-ring. FtsZ is a promising new antimicrobial target, as its inhibition leads to cell death. A precise view of the Z-ring architecture in vivo is essential to understand the mode of action of inhibitory drugs (see T. den Blaauwen, J. M. Andreu, and O. Monasterio, Bioorg Chem 55:27–38, 2014, doi:10.1016/j.bioorg.2014.03.007, for a review on FtsZ inhibitors). This is notably true in ovococcoid bacteria like S. pneumoniae, in which FtsZ is the only known cytoskeletal protein. We have used superresolution microscopy to obtain molecular details of the pneumococcus Z-ring that have so far been inaccessible with conventional microscopy. This study provides a nanoscale description of the Z-ring architecture and remodeling during the division of ovococci.
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84
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Ramírez-Aportela E, López-Blanco JR, Andreu JM, Chacón P. Understanding nucleotide-regulated FtsZ filament dynamics and the monomer assembly switch with large-scale atomistic simulations. Biophys J 2015; 107:2164-76. [PMID: 25418101 DOI: 10.1016/j.bpj.2014.09.033] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/23/2014] [Accepted: 09/30/2014] [Indexed: 01/08/2023] Open
Abstract
Bacterial cytoskeletal protein FtsZ assembles in a head-to-tail manner, forming dynamic filaments that are essential for cell division. Here, we study their dynamics using unbiased atomistic molecular simulations from representative filament crystal structures. In agreement with experimental data, we find different filament curvatures that are supported by a nucleotide-regulated hinge motion between consecutive FtsZ monomers. Whereas GTP-FtsZ filaments bend and twist in a preferred orientation, thereby burying the nucleotide, the differently curved GDP-FtsZ filaments exhibit a heterogeneous distribution of open and closed interfaces between monomers. We identify a coordinated Mg(2+) ion as the key structural element in closing the nucleotide site and stabilizing GTP filaments, whereas the loss of the contacts with loop T7 from the next monomer in GDP filaments leads to open interfaces that are more prone to depolymerization. We monitored the FtsZ monomer assembly switch, which involves opening/closing of the cleft between the C-terminal domain and the H7 helix, and observed the relaxation of isolated and filament minus-end monomers into the closed-cleft inactive conformation. This result validates the proposed switch between the low-affinity monomeric closed-cleft conformation and the active open-cleft FtsZ conformation within filaments. Finally, we observed how the antibiotic PC190723 suppresses the disassembly switch and allosterically induces closure of the intermonomer interfaces, thus stabilizing the filament. Our studies provide detailed structural and dynamic insights into modulation of both the intrinsic curvature of the FtsZ filaments and the molecular switch coupled to the high-affinity end-wise association of FtsZ monomers.
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Affiliation(s)
- Erney Ramírez-Aportela
- Department of Biological Physical Chemistry, Instituto de Química-Física Rocasolano, CSIC, Madrid, Spain; Department of Chemical and Physical Biology, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - José Ramón López-Blanco
- Department of Biological Physical Chemistry, Instituto de Química-Física Rocasolano, CSIC, Madrid, Spain
| | - José Manuel Andreu
- Department of Chemical and Physical Biology, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Pablo Chacón
- Department of Biological Physical Chemistry, Instituto de Química-Física Rocasolano, CSIC, Madrid, Spain.
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85
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Haeusser DP, Rowlett VW, Margolin W. A mutation in Escherichia coli ftsZ bypasses the requirement for the essential division gene zipA and confers resistance to FtsZ assembly inhibitors by stabilizing protofilament bundling. Mol Microbiol 2015; 97:988-1005. [PMID: 26046682 DOI: 10.1111/mmi.13081] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2015] [Indexed: 11/28/2022]
Abstract
The earliest step in Escherichia coli cell division consists of the assembly of FtsZ protein into a proto-ring structure, tethered to the cytoplasmic membrane by FtsA and ZipA. The proto-ring then recruits additional cell division proteins to form the divisome. Previously we described an ftsZ allele, ftsZL169R , which maps to the side of the FtsZ subunit and confers resistance to FtsZ assembly inhibitory factors including Kil of bacteriophage λ. Here we further characterize this allele and its mechanism of resistance. We found that FtsZL169R permits the bypass of the normally essential ZipA, a property previously observed for FtsA gain-of-function mutants such as FtsA* or increased levels of the FtsA-interacting protein FtsN. Similar to FtsA*, FtsZL169R also can partially suppress thermosensitive mutants of ftsQ or ftsK, which encode additional divisome proteins, and confers strong resistance to excess levels of FtsA, which normally inhibit FtsZ ring function. Additional genetic and biochemical assays provide further evidence that FtsZL169R enhances FtsZ protofilament bundling, thereby conferring resistance to assembly inhibitors and bypassing the normal requirement for ZipA. This work highlights the importance of FtsZ protofilament bundling during cell division and its likely role in regulating additional divisome activities.
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Affiliation(s)
- Daniel P Haeusser
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX, 77030, USA
| | - Veronica W Rowlett
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX, 77030, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX, 77030, USA
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86
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Sundararajan K, Miguel A, Desmarais SM, Meier EL, Casey Huang K, Goley ED. The bacterial tubulin FtsZ requires its intrinsically disordered linker to direct robust cell wall construction. Nat Commun 2015; 6:7281. [PMID: 26099469 PMCID: PMC4532373 DOI: 10.1038/ncomms8281] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 04/26/2015] [Indexed: 12/17/2022] Open
Abstract
The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery, and orchestrates membrane and peptidoglycan cell wall invagination. However, the mechanism for FtsZ regulation of peptidoglycan metabolism is unknown. The FtsZ GTPase domain is separated from its membrane-anchoring C-terminal conserved (CTC) peptide by a disordered C-terminal linker (CTL). Here, we investigate CTL function in Caulobacter crescentus. Strikingly, production of FtsZ lacking the CTL (ΔCTL) is lethal: cells become filamentous, form envelope bulges, and lyse, resembling treatment with β-lactam antibiotics. This phenotype is produced by FtsZ polymers bearing the CTC and a CTL shorter than 14 residues. Peptidoglycan synthesis still occurs downstream of ΔCTL, however cells expressing ΔCTL exhibit reduced peptidoglycan crosslinking and longer glycan strands than wildtype. Importantly, midcell proteins are still recruited to sites of ΔCTL assembly. We propose that FtsZ regulates peptidoglycan metabolism through a CTL-dependent mechanism that extends beyond simple protein recruitment.
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Affiliation(s)
- Kousik Sundararajan
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Amanda Miguel
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Samantha M Desmarais
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Elizabeth L Meier
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Kerwyn Casey Huang
- 1] Department of Bioengineering, Stanford University, Stanford, California 94305, USA [2] Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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87
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Dow CE, van den Berg HA, Roper DI, Rodger A. Biological Insights from a Simulation Model of the Critical FtsZ Accumulation Required for Prokaryotic Cell Division. Biochemistry 2015; 54:3803-13. [PMID: 26031209 DOI: 10.1021/acs.biochem.5b00261] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A simulation model of prokaryotic Z-ring assembly, based on the observed behavior of FtsZ in vitro as well as on in vivo parameters, is used to integrate critical processes in cell division. According to the model, the cell's ability to divide depends on a "contraction parameter" (χ) that links the force of contraction to the dynamics of FtsZ. This parameter accurately predicts the outcome of division. Evaluating the GTP binding strength, the FtsZ polymerization rate, and the intrinsic GTP hydrolysis/dissociation activity, we find that inhibition of GTP-FtsZ binding is an inefficient antibacterial target. Furthermore, simulations indicate that the temperature sensitivity of the ftsZ84 mutation arises from the conversion of FtsZ to a dual-specificity NTPase. Finally, the sensitivity to temperature of the rate of ATP hydrolysis, over the critical temperature range, leads us to conclude that the ftsZ84 mutation affects the turnover rate of the Z-ring much less strongly than previously reported.
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Affiliation(s)
- Claire E Dow
- †Molecular Organisation and Assembly in Cells Doctoral Training Centre, Senate House, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Hugo A van den Berg
- ‡Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - David I Roper
- §School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Alison Rodger
- ∥Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom.,⊥Warwick Analytical Science Centre, University of Warwick, Coventry CV4 7AL, United Kingdom
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88
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A multi-layered protein network stabilizes the Escherichia coli FtsZ-ring and modulates constriction dynamics. PLoS Genet 2015; 11:e1005128. [PMID: 25848771 PMCID: PMC4388696 DOI: 10.1371/journal.pgen.1005128] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 03/04/2015] [Indexed: 11/19/2022] Open
Abstract
The prokaryotic tubulin homolog, FtsZ, forms a ring-like structure (FtsZ-ring) at midcell. The FtsZ-ring establishes the division plane and enables the assembly of the macromolecular division machinery (divisome). Although many molecular components of the divisome have been identified and their interactions extensively characterized, the spatial organization of these proteins within the divisome is unclear. Consequently, the physical mechanisms that drive divisome assembly, maintenance, and constriction remain elusive. Here we applied single-molecule based superresolution imaging, combined with genetic and biophysical investigations, to reveal the spatial organization of cellular structures formed by four important divisome proteins in E. coli: FtsZ, ZapA, ZapB and MatP. We show that these interacting proteins are arranged into a multi-layered protein network extending from the cell membrane to the chromosome, each with unique structural and dynamic properties. Further, we find that this protein network stabilizes the FtsZ-ring, and unexpectedly, slows down cell constriction, suggesting a new, unrecognized role for this network in bacterial cell division. Our results provide new insight into the structure and function of the divisome, and highlight the importance of coordinated cell constriction and chromosome segregation. Bacterial cell division is a highly regulated process that must be coordinated with other cellular processes (i.e. DNA replication and chromosome segregation) to promote faithful reproduction. In Escherichia coli, this regulation is most often mediated through the polymerization of the prokaryotic tubulin homolog, FtsZ, which forms a ring-like structure (FtsZ-ring) at midcell. The establishment of the FtsZ-ring marks the site of division and enables the assembly of the macromolecular division machinery (divisome). Here we applied single-molecule based superresolution imaging to reveal the three-dimensional structure of FtsZ in the context of its regulatory proteins: ZapA, ZapB and MatP. We found that these four proteins exist in a multi-layered network that extends from the cell membrane to the chromosome. This layered organization not only helps to stabilize the FtsZ-ring, but also serves to coordinate division with DNA status by influencing constriction rate. Our results not only provide a comprehensive view of the divisome, but also allow new insight to be garnered regarding the structure and function of the divisome.
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89
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Miguel A, Hsin J, Liu T, Tang G, Altman RB, Huang KC. Variations in the binding pocket of an inhibitor of the bacterial division protein FtsZ across genotypes and species. PLoS Comput Biol 2015; 11:e1004117. [PMID: 25811761 PMCID: PMC4374959 DOI: 10.1371/journal.pcbi.1004117] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 01/08/2015] [Indexed: 01/28/2023] Open
Abstract
The recent increase in antibiotic resistance in pathogenic bacteria calls for new approaches to drug-target selection and drug development. Targeting the mechanisms of action of proteins involved in bacterial cell division bypasses problems associated with increasingly ineffective variants of older antibiotics; to this end, the essential bacterial cytoskeletal protein FtsZ is a promising target. Recent work on its allosteric inhibitor, PC190723, revealed in vitro activity on Staphylococcus aureus FtsZ and in vivo antimicrobial activities. However, the mechanism of drug action and its effect on FtsZ in other bacterial species are unclear. Here, we examine the structural environment of the PC190723 binding pocket using PocketFEATURE, a statistical method that scores the similarity between pairs of small-molecule binding sites based on 3D structure information about the local microenvironment, and molecular dynamics (MD) simulations. We observed that species and nucleotide-binding state have significant impacts on the structural properties of the binding site, with substantially disparate microenvironments for bacterial species not from the Staphylococcus genus. Based on PocketFEATURE analysis of MD simulations of S. aureus FtsZ bound to GTP or with mutations that are known to confer PC190723 resistance, we predict that PC190723 strongly prefers to bind Staphylococcus FtsZ in the nucleotide-bound state. Furthermore, MD simulations of an FtsZ dimer indicated that polymerization may enhance PC190723 binding. Taken together, our results demonstrate that a drug-binding pocket can vary significantly across species, genetic perturbations, and in different polymerization states, yielding important information for the further development of FtsZ inhibitors.
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Affiliation(s)
- Amanda Miguel
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Jen Hsin
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Tianyun Liu
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Grace Tang
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Russ B. Altman
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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90
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Jiang C, Caccamo PD, Brun YV. Mechanisms of bacterial morphogenesis: evolutionary cell biology approaches provide new insights. Bioessays 2015; 37:413-25. [PMID: 25664446 DOI: 10.1002/bies.201400098] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
How Darwin's "endless forms most beautiful" have evolved remains one of the most exciting questions in biology. The significant variety of bacterial shapes is most likely due to the specific advantages they confer with respect to the diverse environments they occupy. While our understanding of the mechanisms generating relatively simple shapes has improved tremendously in the last few years, the molecular mechanisms underlying the generation of complex shapes and the evolution of shape diversity are largely unknown. The emerging field of bacterial evolutionary cell biology provides a novel strategy to answer this question in a comparative phylogenetic framework. This relatively novel approach provides hypotheses and insights into cell biological mechanisms, such as morphogenesis, and their evolution that would have been difficult to obtain by studying only model organisms. We discuss the necessary steps, challenges, and impact of integrating "evolutionary thinking" into bacterial cell biology in the genomic era.
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Affiliation(s)
- Chao Jiang
- Department of Biology, Indiana University, Bloomington, IN, USA
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91
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Tao J, Sang Y, Teng Q, Ni J, Yang Y, Tsui SKW, Yao YF. Heat shock proteins IbpA and IbpB are required for NlpI-participated cell division in Escherichia coli. Front Microbiol 2015; 6:51. [PMID: 25699035 PMCID: PMC4316790 DOI: 10.3389/fmicb.2015.00051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 01/15/2015] [Indexed: 11/29/2022] Open
Abstract
Lipoprotein NlpI of Escherichia coli is involved in the cell division, virulence, and bacterial interaction with eukaryotic host cells. To elucidate the functional mechanism of NlpI, we examined how NlpI affects cell division and found that induction of NlpI inhibits nucleoid division and halts cell growth. Consistent with these results, the cell division protein FtsZ failed to localize at the septum but diffused in the cytosol. Elevation of NlpI expression enhanced the transcription and the outer membrane localization of the heat shock protein IbpA and IbpB. Deletion of either ibpA or ibpB abolished the effects of NlpI induction, which could be restored by complementation. The C-terminus of NlpI is critical for the enhancement in IbpA and IbpB production, and the N-terminus of NlpI is required for the outer membrane localization of NlpI, IbpA, and IbpB. Furthermore, NlpI physically interacts with IbpB. These results indicate that over-expression of NlpI can interrupt the nucleoids division and the assembly of FtsZ at the septum, mediated by IbpA/IbpB, suggesting a role of the NlpI/IbpA/IbpB complex in the cell division.
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Affiliation(s)
- Jing Tao
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine Shanghai, China
| | - Yu Sang
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine Shanghai, China
| | - Qihui Teng
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine Shanghai, China
| | - Jinjing Ni
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine Shanghai, China
| | - Yi Yang
- School of Biomedical Sciences, The Chinese University of Hong Kong Hong Kong, China
| | | | - Yu-Feng Yao
- Laboratory of Bacterial Pathogenesis, Department of Microbiology and Immunology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine Shanghai, China
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92
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Broughton CE, Roper DI, Van Den Berg HA, Rodger A. Bacterial cell division: experimental and theoretical approaches to the divisome. Sci Prog 2015; 98:313-45. [PMID: 26790174 PMCID: PMC10365498 DOI: 10.3184/003685015x14461391862881] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cell division is a key event in the bacterial life cycle. It involves constriction at the midcell, so that one cell can give rise to two daughter cells. This constriction is mediated by a ring composed offibrous multimers of the protein FtsZ. However a host of additional factors is involved in the formation and dynamics of this "Z-ring" and this complicated apparatus is collectively known as the "divisome". We review the literature, with an emphasis on mathematical modelling, and show how such theoretical efforts have helped experimentalists to make sense of the at times bewildering data, and plan further experiments.
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93
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Du S, Park KT, Lutkenhaus J. Oligomerization of FtsZ converts the FtsZ tail motif (conserved carboxy-terminal peptide) into a multivalent ligand with high avidity for partners ZipA and SlmA. Mol Microbiol 2014; 95:173-88. [PMID: 25382687 DOI: 10.1111/mmi.12854] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2014] [Indexed: 01/06/2023]
Abstract
A short conserved motif located at the carboxy terminus of FtsZ, referred to here as the CCTP (conserved carboxy-terminal peptide), is required for the interaction of FtsZ with many of its partners. In Escherichia coli interaction of FtsZ with its membrane anchors, ZipA and FtsA, as well as the spatial regulators of Z-ring formation, MinC and SlmA, requires the CCTP. ZipA interacts with FtsZ with high affinity and interacts with the CCTP with low affinity, but the reason for this difference is not clear. In this study, we show that this difference is due to the oligomerization of FtsZ converting the CCTP to a multivalent ligand that binds multiple ZipAs bound to a surface with high avidity. Artificial dimerization of the CCTP is sufficient to increase the affinity for ZipA in vitro. Similar principles apply to the interaction of FtsZ with SlmA. Although done in vitro, these results have implications for the recruitment of FtsZ to the membrane in vivo, the interaction of FtsZ with spatial regulators and the reconstitution of FtsZ systems in vitro.
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Affiliation(s)
- Shishen Du
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
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94
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Szwedziak P, Wang Q, Bharat TAM, Tsim M, Löwe J. Architecture of the ring formed by the tubulin homologue FtsZ in bacterial cell division. eLife 2014; 3:e04601. [PMID: 25490152 PMCID: PMC4383033 DOI: 10.7554/elife.04601] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/08/2014] [Indexed: 12/16/2022] Open
Abstract
Membrane constriction is a prerequisite for cell division. The most common membrane
constriction system in prokaryotes is based on the tubulin homologue FtsZ, whose
filaments in E. coli are anchored to the membrane by FtsA and enable
the formation of the Z-ring and divisome. The precise architecture of the FtsZ ring
has remained enigmatic. In this study, we report three-dimensional arrangements of
FtsZ and FtsA filaments in C. crescentus and E.
coli cells and inside constricting liposomes by means of electron
cryomicroscopy and cryotomography. In vivo and in vitro, the Z-ring is composed of a
small, single-layered band of filaments parallel to the membrane, creating a
continuous ring through lateral filament contacts. Visualisation of the in vitro
reconstituted constrictions as well as a complete tracing of the helical paths of the
filaments with a molecular model favour a mechanism of FtsZ-based membrane
constriction that is likely to be accompanied by filament sliding. DOI:http://dx.doi.org/10.7554/eLife.04601.001 Cell division is the process by which new cells are made. It is therefore vital for
the growth and development, and the regeneration and repair of damaged tissues. When
bacterial and animal cells divide, they must constrict their membrane inwards to
split a single cell into two. In most bacteria, this constriction is guided by a
ring-like structure that contains filaments of a protein called FtsZ. During cell
division, this structure forms around the inside edge of the cell and when it
contracts, it pulls the membrane inwards and causes the cell to constrict and
eventually divide. In recent years, this arrangement of FtsZ filaments has been intensively
investigated, giving rise to various theories about how it is made and how it works:
for example, some recent studies suggested that FtsZ does not form a continuous ring.
Nevertheless, many details about the cell division process remain unknown. Szwedziak, Wang et al. have now investigated this protein ring in two species of
bacteria by turning to advanced forms of microscopy to closely observe its structure
and how it works. This included mapping the ring in three dimensions. Contrary to
earlier reports that the FtsZ ring is discontinuous, in both a bacterium called
Caulobacter crescentus and another called Escherichia
coli, the ring forms a continuous shape made up of overlapping
filaments. Szwedziak, Wang et al. then increased the levels of two of the ring's main
components: the FtsZ protein that forms the filaments and a protein that anchors
these filaments to the cell membrane. This caused the modified cells to constrict and
divide at extra sites, which resulted in the formation of abnormally small cells.
These findings suggest that these two ring components by themselves are able to
generate both the structures and force required for cell constriction. This is
supported by the fact that when they were introduced into artificial cell-like
structures, these proteins spontaneously self-organised into rings and triggered
constriction where they formed. Szwedziak, Wang et al. propose that constriction only starts once the FtsZ protein
forms a closed ring and that the ring's overlapping filaments slide along each other
to further decrease its diameter and constrict the cell. The degree of filament
overlap likely also increases with constriction, requiring filaments to be shortened
to maintain sliding. This shortening, along with sliding, could provide a mechanism
by which to drive the constriction process. This work will be followed by even more detailed studies in order to understand the
process of bacterial cell division at the atomic scale and how the cell's wall is
reshaped during the process. In the long run, intricate knowledge of how a bacterial
cell divides might enable the design of new classes of antibiotics targeting the
molecular machinery involved. DOI:http://dx.doi.org/10.7554/eLife.04601.002
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Affiliation(s)
- Piotr Szwedziak
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Qing Wang
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Tanmay A M Bharat
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Matthew Tsim
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Jan Löwe
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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95
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Structure and function of a spectrin-like regulator of bacterial cytokinesis. Nat Commun 2014; 5:5421. [PMID: 25403286 PMCID: PMC4243239 DOI: 10.1038/ncomms6421] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 09/30/2014] [Indexed: 11/09/2022] Open
Abstract
Bacterial cell division is facilitated by a molecular machine--the divisome--that assembles at mid-cell in dividing cells. The formation of the cytokinetic Z-ring by the tubulin homologue FtsZ is regulated by several factors, including the divisome component EzrA. Here we describe the structure of the 60-kDa cytoplasmic domain of EzrA, which comprises five linear repeats of an unusual triple helical bundle. The EzrA structure is bent into a semicircle, providing the protein with the potential to interact at both N- and C-termini with adjacent membrane-bound divisome components. We also identify at least two binding sites for FtsZ on EzrA and map regions of EzrA that are responsible for regulating FtsZ assembly. The individual repeats, and their linear organization, are homologous to the spectrin proteins that connect actin filaments to the membrane in eukaryotes, and we thus propose that EzrA is the founding member of the bacterial spectrin family.
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96
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Buske PJ, Mittal A, Pappu RV, Levin PA. An intrinsically disordered linker plays a critical role in bacterial cell division. Semin Cell Dev Biol 2014; 37:3-10. [PMID: 25305578 DOI: 10.1016/j.semcdb.2014.09.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 09/13/2014] [Indexed: 02/07/2023]
Abstract
In bacteria, animals, fungi, and many single celled eukaryotes, division is initiated by the formation of a ring of cytoskeletal protein at the nascent division site. In bacteria, the tubulin-like GTPase FtsZ serves as the foundation for the cytokinetic ring. A conserved feature of FtsZ is an intrinsically disordered peptide known as the C-terminal linker. Chimeric experiments suggest the linker acts as a flexible boom allowing FtsZ to associate with the membrane through a conserved C-terminal domain and also modulates interactions both between FtsZ subunits and between FtsZ and modulatory proteins in the cytoplasm.
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Affiliation(s)
- P J Buske
- Department of Cellular and Molecular Pharmacology and The Howard Hughes Medical Institute, University of California, San Francisco, CA, USA
| | - Anuradha Mittal
- Department of Biomedical Engineering & Center for Biological Systems Engineering, Saint Louis, MO 63130, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering & Center for Biological Systems Engineering, Saint Louis, MO 63130, USA
| | - Petra Anne Levin
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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97
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Abstract
The rod is a ubiquitous shape adopted by walled cells from diverse organisms ranging from bacteria to fungi to plants. Although rod-like shapes are found in cells of vastly different sizes and are constructed by diverse mechanisms, the geometric similarities among these shapes across kingdoms suggest that there are common evolutionary advantages, which may result from simple physical principles in combination with chemical and physiological constraints. Here, we review mechanisms of constructing rod-shaped cells and the bases of different biophysical models of morphogenesis, comparing and contrasting model organisms in different kingdoms. We then speculate on possible advantages of the rod shape, and suggest strategies for elucidating the relative importance of each of these advantages.
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98
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Billings G, Ouzounov N, Ursell T, Desmarais SM, Shaevitz J, Gitai Z, Huang KC. De novo morphogenesis in L-forms via geometric control of cell growth. Mol Microbiol 2014; 93:883-96. [PMID: 24995493 DOI: 10.1111/mmi.12703] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2014] [Indexed: 01/06/2023]
Abstract
In virtually all bacteria, the cell wall is crucial for mechanical integrity and for determining cell shape. Escherichia coli's rod-like shape is maintained via the spatiotemporal patterning of cell-wall synthesis by the actin homologue MreB. Here, we transiently inhibited cell-wall synthesis in E. coli to generate cell-wall-deficient, spherical L-forms, and found that they robustly reverted to a rod-like shape within several generations after inhibition cessation. The chemical composition of the cell wall remained essentially unchanged during this process, as indicated by liquid chromatography. Throughout reversion, MreB localized to inwardly curved regions of the cell, and fluorescent cell wall labelling revealed that MreB targets synthesis to those regions. When exposed to the MreB inhibitor A22, reverting cells regrew a cell wall but failed to recover a rod-like shape. Our results suggest that MreB provides the geometric measure that allows E. coli to actively establish and regulate its morphology.
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Affiliation(s)
- Gabriel Billings
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
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99
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Abstract
Mycobacterium tuberculosis, which is the aetiological agent of tuberculosis, owes much of its success as a pathogen to its unique cell wall and unusual mechanism of growth, which facilitate its adaptation to the human host and could have a role in clinical latency. Asymmetric growth and division increase population heterogeneity, which may promote antibiotic tolerance and the fitness of single cells. In this Review, we describe the unusual mechanisms of mycobacterial growth, cell wall biogenesis and division, and discuss how these processes might affect the survival of M. tuberculosis in vivo and contribute to the persistence of infection.
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100
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Peptidoglycan synthesis machinery in Agrobacterium tumefaciens during unipolar growth and cell division. mBio 2014; 5:e01219-14. [PMID: 24865559 PMCID: PMC4045076 DOI: 10.1128/mbio.01219-14] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The synthesis of peptidoglycan (PG) in bacteria is a crucial process controlling cell shape and vitality. In contrast to bacteria such as Escherichia coli that grow by dispersed lateral insertion of PG, little is known of the processes that direct polar PG synthesis in other bacteria such as the Rhizobiales. To better understand polar growth in the Rhizobiales Agrobacterium tumefaciens, we first surveyed its genome to identify homologs of (~70) well-known PG synthesis components. Since most of the canonical cell elongation components are absent from A. tumefaciens, we made fluorescent protein fusions to other putative PG synthesis components to assay their subcellular localization patterns. The cell division scaffolds FtsZ and FtsA, PBP1a, and a Rhizobiales- and Rhodobacterales-specific l,d-transpeptidase (LDT) all associate with the elongating cell pole. All four proteins also localize to the septum during cell division. Examination of the dimensions of growing cells revealed that new cell compartments gradually increase in width as they grow in length. This increase in cell width is coincident with an expanded region of LDT-mediated PG synthesis activity, as measured directly through incorporation of exogenous d-amino acids. Thus, unipolar growth in the Rhizobiales is surprisingly dynamic and represents a significant departure from the canonical growth mechanism of E. coli and other well-studied bacilli. Many rod-shaped bacteria, including pathogens such as Brucella and Mycobacterium, grow by adding new material to their cell poles, and yet the proteins and mechanisms contributing to this process are not yet well defined. The polarly growing plant pathogen Agrobacterium tumefaciens was used as a model bacterium to explore these polar growth mechanisms. The results obtained indicate that polar growth in this organism is facilitated by repurposed cell division components and an otherwise obscure class of alternative peptidoglycan transpeptidases (l,d-transpeptidases). This growth results in dynamically changing cell widths as the poles expand to maturity and contrasts with the tightly regulated cell widths characteristic of canonical rod-shaped growth. Furthermore, the abundance and/or activity of l,d-transpeptidases appears to associate with polar growth strategies, suggesting that these enzymes may serve as attractive targets for specifically inhibiting growth of Rhizobiales, Actinomycetales, and other polarly growing bacterial pathogens.
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