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Germán Rivas - One of the best experts on this subject based on the ideXlab platform.
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bacterial FtsZ Protein forms phase separated condensates with its nucleoid associated inhibitor slma
EMBO Reports, 2019Co-Authors: Begoña Monterroso, William Margolin, Silvia Zorrilla, Marta Sobrinossanguino, Miguel Angel Roblesramos, Marina Lopezalvarez, Christine D Keating, Germán RivasAbstract:Macromolecular condensation resulting from biologically regulated liquid-liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for cell physiology and pathology. Despite their small size, bacterial cells are also organized by Proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding-induced condensates, reminiscent of those observed for eukaryotic Proteins. Formation of these FtsZ-rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP-driven assembly to form Protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoProtein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.
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Nucleotide and receptor density modulate binding of bacterial division FtsZ Protein to ZipA containing lipid-coated microbeads.
Scientific reports, 2017Co-Authors: Marta Sobrinos-sanguino, Silvia Zorrilla, Begoña Monterroso, Allen P. Minton, Germán RivasAbstract:ZipA Protein from Escherichia coli is one of the essential components of the division proto-ring that provides membrane tethering to the septation FtsZ Protein. A sedimentation assay was used to measure the equilibrium binding of FtsZ-GDP and FtsZ-GTP to ZipA immobilized at controlled densities on the surface of microbeads coated with a phospholipid mixture resembling the composition of E. coli membrane. We found that for both nucleotide-bound species, the amount of bound FtsZ exceeds the monolayer capacity of the ZipA immobilized beads at high concentrations of free FtsZ. In the case of FtsZ-GDP, equilibrium binding does not appear to be saturable, whereas in the case of FtsZ-GTP equilibrium binding appears to be saturable. The difference between the two modes of binding is attributed to the difference between the composition of oligomers of free FtsZ-GDP and free FtsZ-GTP formed in solution.
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microenvironments created by liquid liquid phase transition control the dynamic distribution of bacterial division FtsZ Protein
Scientific Reports, 2016Co-Authors: Begoña Monterroso, Silvia Zorrilla, Marta Sobrinossanguino, Christine D Keating, Germán RivasAbstract:The influence of membrane-free microcompartments resulting from crowding-induced liquid/liquid phase separation (LLPS) on the dynamic spatial organization of FtsZ, the main component of the bacterial division machinery, has been studied using several LLPS systems. The GTP-dependent assembly cycle of FtsZ is thought to be crucial for the formation of the septal ring, which is highly regulated in time and space. We found that FtsZ accumulates in one of the phases and/or at the interface, depending on the system composition and on the oligomerization state of the Protein. These results were observed both in bulk LLPS and in lipid-stabilized, phase-separated aqueous microdroplets. The visualization of the droplets revealed that both the location and structural arrangement of FtsZ filaments is determined by the nature of the LLPS. Relocation upon depolymerization of the dynamic filaments suggests the Protein may shift among microenvironments in response to changes in its association state. The existence of these dynamic compartments driven by phase transitions can alter the local composition and reactivity of FtsZ during its life cycle acting as a nonspecific modulating factor of cell function.
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the nucleoid occlusion slma Protein accelerates the disassembly of the FtsZ Protein polymers without affecting their gtpase activity
PLOS ONE, 2015Co-Authors: Elisa J Cabre, Silvia Zorrilla, Begoña Monterroso, Miguel Vicente, Carlos Alfonso, Alicia Sanchezgorostiaga, Belen Reija, Mercedes Jimenez, Germán RivasAbstract:Division site selection is achieved in bacteria by different mechanisms, one of them being nucleoid occlusion, which prevents Z-ring assembly nearby the chromosome. Nucleoid occlusion in E. coli is mediated by SlmA, a sequence specific DNA binding Protein that antagonizes FtsZ assembly. Here we show that, when bound to its specific target DNA sequences (SBS), SlmA reduces the lifetime of the FtsZ protofilaments in solution and of the FtsZ bundles when located inside permeable giant vesicles. This effect appears to be essentially uncoupled from the GTPase activity of the FtsZ protofilaments, which is insensitive to the presence of SlmA·SBS. The interaction of SlmA·SBS with either FtsZ protofilaments containing GTP or FtsZ oligomers containing GDP results in the disassembly of FtsZ polymers. We propose that SlmA·SBS complexes control the polymerization state of FtsZ by accelerating the disassembly of the FtsZ polymers leading to their fragmentation into shorter species that are still able to hydrolyze GTP at the same rate. SlmA defines therefore a new class of inhibitors of the FtsZ ring different from the SOS response regulator SulA and from the moonlighting enzyme OpgH, inhibitors of the GTPase activity. SlmA also shows differences compared with MinC, the inhibitor of the division site selection Min system, which shortens FtsZ protofilaments by interacting with the GDP form of FtsZ.
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Reconstitution of cytoskeletal Protein assemblies for large-scale membrane transformation.
Current opinion in chemical biology, 2014Co-Authors: Germán Rivas, Sven K. Vogel, Petra SchwilleAbstract:Membranes determine two-dimensional and three-dimensional biochemical reaction spaces in living systems. Defining size and shape of surfaces and volumes encompassed by membrane is of key importance for cellular metabolism and homeostasis, and the maintenance and controlled transformation of membrane shapes are coordinated by a large number of different Protein assemblies. The orchestration of spatial elements over distances orders of magnitudes larger than Protein molecules, as required for cell division, is a particularly challenging task, requiring large-scale ordered Protein filaments and networks. The structure and function of these networks, particularly of cytoskeletal elements, have been characterized extensively in cells and reconstituted systems. However, their co-reconstitution with membranes from the bottom-up under defined conditions, to elucidate their mode of action in detail, is still a relatively new field of research. In this short review, we discuss recent approaches and achievements with regard to the study of cytoskeletal Protein assemblies on model membranes, with specific focus on contractile elements as those based on the bacterial division FtsZ Protein and eukaryotic actomyosin structures.
William Margolin - One of the best experts on this subject based on the ideXlab platform.
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Bacterial Division: Journey to the Center of the Cell
Current biology : CB, 2020Co-Authors: William MargolinAbstract:Summary Most bacteria divide by corralling the tubulin-like FtsZ Protein to mid-cell, where it assembles into a ring of treadmilling membrane-tethered oligomers. A study in this issue reveals new details about how FtsZ finds its way to the ring.
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bacterial FtsZ Protein forms phase separated condensates with its nucleoid associated inhibitor slma
EMBO Reports, 2019Co-Authors: Begoña Monterroso, William Margolin, Silvia Zorrilla, Marta Sobrinossanguino, Miguel Angel Roblesramos, Marina Lopezalvarez, Christine D Keating, Germán RivasAbstract:Macromolecular condensation resulting from biologically regulated liquid-liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for cell physiology and pathology. Despite their small size, bacterial cells are also organized by Proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding-induced condensates, reminiscent of those observed for eukaryotic Proteins. Formation of these FtsZ-rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP-driven assembly to form Protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoProtein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.
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Bacterial Division: FtsZ Treadmills to Build a Beautiful Wall
Current biology : CB, 2017Co-Authors: Kara M. Schoenemann, William MargolinAbstract:Summary The tubulin-like FtsZ Protein polymerizes into a contractile ring structure required for cytokinesis in most bacteria. Two new studies report that FtsZ polymers move around the ring by treadmilling, which guides and regulates the inward growth of the septal wall.
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FtsZ and the division of prokaryotic cells and organelles
Nature reviews. Molecular cell biology, 2005Co-Authors: William MargolinAbstract:Binary fission of many prokaryotes as well as some eukaryotic organelles depends on the FtsZ Protein, which self-assembles into a membrane-associated ring structure early in the division process. FtsZ is homologous to tubulin, the building block of the microtubule cytoskeleton in eukaryotes. Recent advances in genomics and cell-imaging techniques have paved the way for the remarkable progress in our understanding of fission in bacteria and organelles.
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Interaction of FtsZ Protein with a DPPE Langmuir film
Colloids and Surfaces B: Biointerfaces, 2002Co-Authors: Stéphane Alexandre, William Margolin, G. Colé, S. Coutard, Chantal Monnier, Vic Norris, Jean-marc ValletonAbstract:Abstract FtsZ is the key Protein in cell division in bacteria. We have proposed that lipid domains in the cytoplasmic membrane play a role in the localisation of FtsZ. In order to test this hypothesis, we used a model system based on Langmuir films to simulate the bacterial membrane. In this simple system we used a single phospholipid, dipalmytoylphosphatidylethanolamine, which is the major constituent of the inner membrane in Escherichia coli. The first results show clearly the importance of the GTP-controlled assembly process in the appearance of circular or fibrillar structures.
Begoña Monterroso - One of the best experts on this subject based on the ideXlab platform.
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bacterial FtsZ Protein forms phase separated condensates with its nucleoid associated inhibitor slma
EMBO Reports, 2019Co-Authors: Begoña Monterroso, William Margolin, Silvia Zorrilla, Marta Sobrinossanguino, Miguel Angel Roblesramos, Marina Lopezalvarez, Christine D Keating, Germán RivasAbstract:Macromolecular condensation resulting from biologically regulated liquid-liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for cell physiology and pathology. Despite their small size, bacterial cells are also organized by Proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding-induced condensates, reminiscent of those observed for eukaryotic Proteins. Formation of these FtsZ-rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP-driven assembly to form Protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoProtein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.
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Nucleotide and receptor density modulate binding of bacterial division FtsZ Protein to ZipA containing lipid-coated microbeads.
Scientific reports, 2017Co-Authors: Marta Sobrinos-sanguino, Silvia Zorrilla, Begoña Monterroso, Allen P. Minton, Germán RivasAbstract:ZipA Protein from Escherichia coli is one of the essential components of the division proto-ring that provides membrane tethering to the septation FtsZ Protein. A sedimentation assay was used to measure the equilibrium binding of FtsZ-GDP and FtsZ-GTP to ZipA immobilized at controlled densities on the surface of microbeads coated with a phospholipid mixture resembling the composition of E. coli membrane. We found that for both nucleotide-bound species, the amount of bound FtsZ exceeds the monolayer capacity of the ZipA immobilized beads at high concentrations of free FtsZ. In the case of FtsZ-GDP, equilibrium binding does not appear to be saturable, whereas in the case of FtsZ-GTP equilibrium binding appears to be saturable. The difference between the two modes of binding is attributed to the difference between the composition of oligomers of free FtsZ-GDP and free FtsZ-GTP formed in solution.
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microenvironments created by liquid liquid phase transition control the dynamic distribution of bacterial division FtsZ Protein
Scientific Reports, 2016Co-Authors: Begoña Monterroso, Silvia Zorrilla, Marta Sobrinossanguino, Christine D Keating, Germán RivasAbstract:The influence of membrane-free microcompartments resulting from crowding-induced liquid/liquid phase separation (LLPS) on the dynamic spatial organization of FtsZ, the main component of the bacterial division machinery, has been studied using several LLPS systems. The GTP-dependent assembly cycle of FtsZ is thought to be crucial for the formation of the septal ring, which is highly regulated in time and space. We found that FtsZ accumulates in one of the phases and/or at the interface, depending on the system composition and on the oligomerization state of the Protein. These results were observed both in bulk LLPS and in lipid-stabilized, phase-separated aqueous microdroplets. The visualization of the droplets revealed that both the location and structural arrangement of FtsZ filaments is determined by the nature of the LLPS. Relocation upon depolymerization of the dynamic filaments suggests the Protein may shift among microenvironments in response to changes in its association state. The existence of these dynamic compartments driven by phase transitions can alter the local composition and reactivity of FtsZ during its life cycle acting as a nonspecific modulating factor of cell function.
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the nucleoid occlusion slma Protein accelerates the disassembly of the FtsZ Protein polymers without affecting their gtpase activity
PLOS ONE, 2015Co-Authors: Elisa J Cabre, Silvia Zorrilla, Begoña Monterroso, Miguel Vicente, Carlos Alfonso, Alicia Sanchezgorostiaga, Belen Reija, Mercedes Jimenez, Germán RivasAbstract:Division site selection is achieved in bacteria by different mechanisms, one of them being nucleoid occlusion, which prevents Z-ring assembly nearby the chromosome. Nucleoid occlusion in E. coli is mediated by SlmA, a sequence specific DNA binding Protein that antagonizes FtsZ assembly. Here we show that, when bound to its specific target DNA sequences (SBS), SlmA reduces the lifetime of the FtsZ protofilaments in solution and of the FtsZ bundles when located inside permeable giant vesicles. This effect appears to be essentially uncoupled from the GTPase activity of the FtsZ protofilaments, which is insensitive to the presence of SlmA·SBS. The interaction of SlmA·SBS with either FtsZ protofilaments containing GTP or FtsZ oligomers containing GDP results in the disassembly of FtsZ polymers. We propose that SlmA·SBS complexes control the polymerization state of FtsZ by accelerating the disassembly of the FtsZ polymers leading to their fragmentation into shorter species that are still able to hydrolyze GTP at the same rate. SlmA defines therefore a new class of inhibitors of the FtsZ ring different from the SOS response regulator SulA and from the moonlighting enzyme OpgH, inhibitors of the GTPase activity. SlmA also shows differences compared with MinC, the inhibitor of the division site selection Min system, which shortens FtsZ protofilaments by interacting with the GDP form of FtsZ.
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combined analytical ultracentrifugation light scattering and fluorescence spectroscopy studies on the functional associations of the bacterial division FtsZ Protein
Methods, 2013Co-Authors: Begoña Monterroso, Silvia Zorrilla, Carlos Alfonso, Germán RivasAbstract:The combined application of different biophysical techniques - analytical ultracentrifugation, light scattering and fluorescence-based assays - to study the ligand-linked self-association and assembly properties of the cell division Protein FtsZ from Escherichia coli is described. These reactions are thought to be important for the formation of the dynamic division ring that drives bacterial cytokinesis. In addition, the use of this orthogonal experimental approach to measure the interactions between FtsZ oligomers (GDP forms) and polymers (GTP forms) with two variants (a soluble form and a full-length Protein incorporated in phospholipid bilayer nanodiscs) of the ZipA Protein, which provides membrane tethering to FtsZ, is described as well. The power of a global analysis of the results obtained from complementary biophysical methods to discriminate among alternative self- and hetero-associating schemes and to propose a more robust description of the association reactions involved is emphasized. This orthogonal approach will contribute to complete our quantitative understanding of the initial events of bacterial division.
Silvia Zorrilla - One of the best experts on this subject based on the ideXlab platform.
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bacterial FtsZ Protein forms phase separated condensates with its nucleoid associated inhibitor slma
EMBO Reports, 2019Co-Authors: Begoña Monterroso, William Margolin, Silvia Zorrilla, Marta Sobrinossanguino, Miguel Angel Roblesramos, Marina Lopezalvarez, Christine D Keating, Germán RivasAbstract:Macromolecular condensation resulting from biologically regulated liquid-liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for cell physiology and pathology. Despite their small size, bacterial cells are also organized by Proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding-induced condensates, reminiscent of those observed for eukaryotic Proteins. Formation of these FtsZ-rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP-driven assembly to form Protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoProtein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.
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Nucleotide and receptor density modulate binding of bacterial division FtsZ Protein to ZipA containing lipid-coated microbeads.
Scientific reports, 2017Co-Authors: Marta Sobrinos-sanguino, Silvia Zorrilla, Begoña Monterroso, Allen P. Minton, Germán RivasAbstract:ZipA Protein from Escherichia coli is one of the essential components of the division proto-ring that provides membrane tethering to the septation FtsZ Protein. A sedimentation assay was used to measure the equilibrium binding of FtsZ-GDP and FtsZ-GTP to ZipA immobilized at controlled densities on the surface of microbeads coated with a phospholipid mixture resembling the composition of E. coli membrane. We found that for both nucleotide-bound species, the amount of bound FtsZ exceeds the monolayer capacity of the ZipA immobilized beads at high concentrations of free FtsZ. In the case of FtsZ-GDP, equilibrium binding does not appear to be saturable, whereas in the case of FtsZ-GTP equilibrium binding appears to be saturable. The difference between the two modes of binding is attributed to the difference between the composition of oligomers of free FtsZ-GDP and free FtsZ-GTP formed in solution.
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microenvironments created by liquid liquid phase transition control the dynamic distribution of bacterial division FtsZ Protein
Scientific Reports, 2016Co-Authors: Begoña Monterroso, Silvia Zorrilla, Marta Sobrinossanguino, Christine D Keating, Germán RivasAbstract:The influence of membrane-free microcompartments resulting from crowding-induced liquid/liquid phase separation (LLPS) on the dynamic spatial organization of FtsZ, the main component of the bacterial division machinery, has been studied using several LLPS systems. The GTP-dependent assembly cycle of FtsZ is thought to be crucial for the formation of the septal ring, which is highly regulated in time and space. We found that FtsZ accumulates in one of the phases and/or at the interface, depending on the system composition and on the oligomerization state of the Protein. These results were observed both in bulk LLPS and in lipid-stabilized, phase-separated aqueous microdroplets. The visualization of the droplets revealed that both the location and structural arrangement of FtsZ filaments is determined by the nature of the LLPS. Relocation upon depolymerization of the dynamic filaments suggests the Protein may shift among microenvironments in response to changes in its association state. The existence of these dynamic compartments driven by phase transitions can alter the local composition and reactivity of FtsZ during its life cycle acting as a nonspecific modulating factor of cell function.
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the nucleoid occlusion slma Protein accelerates the disassembly of the FtsZ Protein polymers without affecting their gtpase activity
PLOS ONE, 2015Co-Authors: Elisa J Cabre, Silvia Zorrilla, Begoña Monterroso, Miguel Vicente, Carlos Alfonso, Alicia Sanchezgorostiaga, Belen Reija, Mercedes Jimenez, Germán RivasAbstract:Division site selection is achieved in bacteria by different mechanisms, one of them being nucleoid occlusion, which prevents Z-ring assembly nearby the chromosome. Nucleoid occlusion in E. coli is mediated by SlmA, a sequence specific DNA binding Protein that antagonizes FtsZ assembly. Here we show that, when bound to its specific target DNA sequences (SBS), SlmA reduces the lifetime of the FtsZ protofilaments in solution and of the FtsZ bundles when located inside permeable giant vesicles. This effect appears to be essentially uncoupled from the GTPase activity of the FtsZ protofilaments, which is insensitive to the presence of SlmA·SBS. The interaction of SlmA·SBS with either FtsZ protofilaments containing GTP or FtsZ oligomers containing GDP results in the disassembly of FtsZ polymers. We propose that SlmA·SBS complexes control the polymerization state of FtsZ by accelerating the disassembly of the FtsZ polymers leading to their fragmentation into shorter species that are still able to hydrolyze GTP at the same rate. SlmA defines therefore a new class of inhibitors of the FtsZ ring different from the SOS response regulator SulA and from the moonlighting enzyme OpgH, inhibitors of the GTPase activity. SlmA also shows differences compared with MinC, the inhibitor of the division site selection Min system, which shortens FtsZ protofilaments by interacting with the GDP form of FtsZ.
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combined analytical ultracentrifugation light scattering and fluorescence spectroscopy studies on the functional associations of the bacterial division FtsZ Protein
Methods, 2013Co-Authors: Begoña Monterroso, Silvia Zorrilla, Carlos Alfonso, Germán RivasAbstract:The combined application of different biophysical techniques - analytical ultracentrifugation, light scattering and fluorescence-based assays - to study the ligand-linked self-association and assembly properties of the cell division Protein FtsZ from Escherichia coli is described. These reactions are thought to be important for the formation of the dynamic division ring that drives bacterial cytokinesis. In addition, the use of this orthogonal experimental approach to measure the interactions between FtsZ oligomers (GDP forms) and polymers (GTP forms) with two variants (a soluble form and a full-length Protein incorporated in phospholipid bilayer nanodiscs) of the ZipA Protein, which provides membrane tethering to FtsZ, is described as well. The power of a global analysis of the results obtained from complementary biophysical methods to discriminate among alternative self- and hetero-associating schemes and to propose a more robust description of the association reactions involved is emphasized. This orthogonal approach will contribute to complete our quantitative understanding of the initial events of bacterial division.
Lili Niu - One of the best experts on this subject based on the ideXlab platform.
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Single-Molecule Dynamics of FtsZ During Cell Division
Biophysical Journal, 2011Co-Authors: Lili NiuAbstract:Escherichia coli cell division is initiated by the formation of FtsZ-ring structure at the middle of cell body while the internal mechanisms and Min system regulate the special and temporal localization of FtsZ Protein. During division process the FtsZ Protein interacts with many other division-involved or -associated molecules, which are located in cytoplasm, inner membrane and periplasm, expecting the variation in the dynamics of FtsZ-ring structure and molecule itself in wild and mutant types. We studied the dynamics of FtsZ-ring width during different stages of cell cycle by using photoactivated localization microscopy (PALM) technique. In addition, tracking individual FtsZ molecules in live E. coli cell expressing with or without their interacting molecules we measured the difference in physical parameters such as diffusion coefficient and local compartment size. Preliminary data shows the width of Z-ring increases during Z-ring development. The diffusion coefficient of filamentous FtsZ molecule is 0.017 ± 0.0012 μm2/s (n = 332) and the diffusion coefficient of globular FtsZ is 0.75 ± 0.04 μm2/s (n = 30).
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investigating intracellular dynamics of FtsZ cytoskeleton with photoactivation single molecule tracking
Biophysical Journal, 2008Co-Authors: Lili NiuAbstract:Using photoactivatable fluorescent Protein as an intracellular Protein label for single-molecule tracking offers several advantages over the traditional methods. Here we demonstrate the technique of photoactivation single-molecule tracking by investigating the mobility dynamics of intracellular FtsZ Protein molecules in live Escherichia coli cells. FtsZ is a prokaryotic cytoskeleton Protein (a homolog of tubulin) and plays important roles in cytokinesis. We demonstrate two heterogeneous subpopulations of FtsZ molecules with distinct diffusional dynamics. The FtsZ molecules forming the Z-rings near the center of the cell were mostly stationary, consistent with the assumption that they are within polymeric filamentous structures. The rest of the FtsZ molecules, on the other hand, undergo Brownian motion spanning the whole cell length. Surprisingly, the diffusion of FtsZ is spatially restricted to helical-shaped regions, implying an energy barrier for free diffusion. Consistently, the measured mean-square displacements of FtsZ showed anomalous diffusion characteristics. These results demonstrated the feasibility and advantages of photoactivation single-molecule tracking, and suggested new levels of complexity in the prokaryotic membrane organization.
