Novel coiled‐coil cell division factor ZapB stimulates Z ring assembly and cell division

Ebersbach, Gitte; Galli, Elisa; Møller‐Jensen, Jakob; Löwe, Jan; Gerdes, Kenn

doi:10.1111/j.1365-2958.2008.06190.x

Cited by 118 publications

(172 citation statements)

References 63 publications

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“…ZapA localizes to the midcell dependent on a direct interaction with FtsZ and remains dynamically associated with the cytokinetic machinery throughout the cell cycle but is not essential for cell division or viability (Fig. 2) (83,(85)(86)(87).…”

Section: Zapamentioning

confidence: 99%

“…The gene encoding ZapB, which is restricted to the gammaproteobacterial class, was initially isolated in a plasmid destabilization screen to identify host factors that in multicopy would interfere with plasmid partitioning systems (86). ZapB was subsequently determined to be a Z ring stabilizer that colocalizes with FtsZ at midcell and is recruited to the divisome by ZapA ( Fig.…”

Section: Zapbmentioning

confidence: 99%

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FtsZ Ring Stability: of Bundles, Tubules, Crosslinks, and Curves

2013

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The first step in bacterial cytokinesis is the assembly of a stable but dynamic cytokinetic ring made up of the essential tubulin homolog FtsZ at the future site of division. Although FtsZ and its role in cytokinesis have been studied extensively, the precise architecture of the in vivo medial FtsZ ring (Z ring) is not well understood. Recent advances in superresolution imaging suggest that the Z ring comprises short, discontinuous, and loosely bundled FtsZ polymers, some of which are tethered to the membrane. A diverse array of regulatory proteins modulate the assembly, stability, and disassembly of the Z ring via direct interactions with FtsZ. Negative regulators of FtsZ play a critical role in ensuring the accurate positioning of FtsZ at the future site of division and in maintaining Z ring dynamics by controlling FtsZ polymer assembly/disassembly processes. Positive regulators of FtsZ are essential for tethering FtsZ polymers to the membrane and promoting the formation of stabilizing lateral interactions, permitting assembly of a mature Z ring. The past decade has seen the identification of several factors that promote FtsZ assembly, presumably through a variety of distinct molecular mechanisms. While a few of these proteins are broadly conserved, many positive regulators of FtsZ assembly are limited to small groups of closely related organisms, suggesting that FtsZ assembly is differentially modulated across bacterial species. In this review, we focus on the roles of positive regulators in Z ring assembly and in maintaining the integrity of the cytokinetic ring during the early stages of division. Bacterial cytokinesis is mediated by a macromolecular protein machine that is accurately positioned in space and time during the cell cycle. The earliest defined event during cytokinesis is the assembly of a polymeric FtsZ structure at the site of future division known as the FtsZ ring, or Z ring (1). The Z ring serves as a scaffold for the recruitment of other division proteins (2-5). FtsZ, a tubulin homolog, forms homopolymeric linear protofilaments upon binding GTP, and these filaments subsequently disassemble upon hydrolysis of the bound nucleotide (6-9). Approximately 30% of cellular FtsZ is present in the ring, and fluorescence recovery after photobleaching (FRAP) studies reveal that there is dynamic exchange between FtsZ molecules in the ring polymers and FtsZ monomers or short oligomers in the cytoplasm (10, 11).In Escherichia coli and Bacillus subtilis, cytokinesis can be separated chronologically into the following three steps: (i) assembly and stabilization of the Z ring at the future division site and, following a lag, (ii) recruitment of downstream division proteins, many of which are essential to form a constriction-competent division complex, and lastly, (iii) constriction of the Z ring coordinated with synthesis and splitting of septal peptidoglycan, leading to invagination of the cell membrane and division into two daughter cells (Fig. 1A) (2, 12, 13). The force required for constriction is likely...

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Section: Zapamentioning

confidence: 99%

Section: Zapbmentioning

confidence: 99%

FtsZ Ring Stability: of Bundles, Tubules, Crosslinks, and Curves

2013

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“…The assembly and stabilization of FtsZ polymers in the proto-ring are regulated by the Zap proteins (ZapA, ZapB, ZapC, and ZapD), which exhibit functionally redundant roles in binding and bundling polymeric FtsZ (32,[40][41][42][43][44][45][46]. These proteins act at midcell, promoting the transition of FtsZ polymers from a helical band into a compact ring by cooperatively stimulating the lateral association of protofilaments (47, 48).…”

Section: The Proto-ring: the Scaffold Of The Divisomementioning

confidence: 99%

In the Beginning, Escherichia coli Assembled the Proto-ring: An Initial Phase of Division

Rico

Krupka²,

Vicente

2013

Journal of Biological Chemistry

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Cell division in Escherichia coli begins by assembling three proteins, FtsZ, FtsA, and ZipA, to form a proto-ring at midcell. These proteins nucleate an assembly of at least 35 components, the divisome. The structuring of FtsZ to form a ring and the processes that effect constriction have been explained by alternative but not mutually exclusive mechanisms. We discuss how FtsA and ZipA provide anchoring of the cytoplasmic FtsZ to the membrane and how a temporal sequence of alternative protein interactions may operate in the maturation and stability of the proto-ring. How the force needed for constriction is generated and how the proto-ring proteins relate to peptidoglycan synthesis remain as the main challenges for future research. Overview of SeptationCell division is the last event in the bacterial cell cycle. It takes place by producing a rigid transversal septum after the growth processes fully duplicate the contents of the cell. Septation is always preceded by segregation of the duplicated nucleoids, ensuring that each of the daughter cells contains a fully replicated chromosome. Specialized molecules control the positioning of the division machinery at midcell, preventing any harmful fragmentation that septum progression could cause on unsegregated nucleoids.The division machinery, the divisome, establishes a complex interacting network together with DNA, lipids, and peptidoglycan components. It comprises a variable number of proteins, depending on the bacterial species. These proteins have redundant multiple functions and connections serving as safeguards to complete division and to guarantee the efficiency and versatility of the process. Altogether, an efficient division process allows the proliferation of bacteria under a variety of conditions, and it is one of the reasons for their success in the environment. Free-living bacteria, such as Escherichia coli, have more elaborated divisomes, whereas those that need to grow as intracellular parasites, as such Mycoplasma genitalium, have streamlined ones (1, 2).The structure of the E. coli divisome as revealed by immunofluorescence images of dividing cells is called the division ring (3). For its assembly, three essential proteins, FtsZ, FtsA, and ZipA, are first gathered at midcell, forming a proto-ring attached to the inner membrane ( Fig. 1) (4). In the proto-ring structure, the cytoplasmic GTPase FtsZ is anchored to the membrane by its interaction with ZipA and FtsA. ZipA is a bitopic protein containing a transmembrane domain (5). FtsA is a protein of the actin family that associates with the membrane by a short amphipathic helix (6, 7). The assembly of the FtsZ ring is dependent on a continuous energy supply. The FtsZ ring requires either ZipA or FtsA (8). Although it can be formed in the presence of either of them, division is affected unless both are present (9). A maturation period takes place after the protoring is assembled and before the rest of the divisome proteins become incorporated (10). During maturation, the proto-ring assembly is not stable...

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“…In E. coli, this process is mediated by FtsZ-associated proteins (Zap proteins). The first Zap proteins recruited during divisome assembly are ZapA, ZapB, ZapC, and ZapD and are predicted to have overlapping functions (17)(18)(19)(20)(21). These Zap proteins stabilize FtsZ filaments prior to cell division by slowing depolymerization, thereby inhibiting GTPase activity (17,19,21,22).…”

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confidence: 99%

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

et al. 2016

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Bacterial cell division is an essential and highly coordinated process. It requires the polymerization of the tubulin homologue FtsZ to form a dynamic ring (Z-ring) at midcell. Z-ring formation relies on a group of FtsZ-associated proteins (Zap) for stability throughout the process of division. In Escherichia coli, there are currently five Zap proteins (ZapA through ZapE), of which four (ZapA, ZapB, ZapC, and ZapD) are small soluble proteins that act to bind and bundle FtsZ filaments. In particular, ZapD forms a functional dimer and interacts with the C-terminal tail of FtsZ, but little is known about its structure and mechanism of action. Here, we present the crystal structure of Escherichia coli ZapD and show it forms a symmetrical dimer with centrally located ␣-helices flanked by ␤-sheet domains. Based on the structure of ZapD and its chemical cross-linking to FtsZ, we targeted nine charged ZapD residues for modification by site-directed mutagenesis. Using in vitro FtsZ sedimentation assays, we show that residues R56, R221, and R225 are important for bundling FtsZ filaments, while transmission electron microscopy revealed that altering these residues results in different FtsZ bundle morphology compared to those of filaments bundled with wild-type ZapD. ZapD residue R116 also showed altered FtsZ bundle morphology but levels of FtsZ bundling similar to that of wild-type ZapD. Together, these results reveal that ZapD residues R116, R221, and R225 likely participate in forming a positively charged binding pocket that is critical for bundling FtsZ filaments. IMPORTANCEZ-ring assembly underpins the formation of the essential cell division complex known as the divisome and is required for recruitment of downstream cell division proteins. ZapD is one of several proteins in E. coli that associates with the Z-ring to promote FtsZ bundling and aids in the overall fitness of the division process. In the present study, we describe the dimeric structure of E. coli ZapD and identify residues that are critical for FtsZ bundling. Together, these results advance our understanding about the formation and dynamics of the Z-ring prior to bacterial cell division. Bacterial cell division is an essential and complex process that requires the coordinated assembly of a multiprotein molecular machine termed the divisome. The divisome is responsible for constriction of the inner and outer membranes, synthesis of septal peptidoglycan, and subsequent septum formation. In Escherichia coli, divisome proteins are recruited in a hierarchical manner and can be divided into three main groups based on their order of assembly: (i) the proto-ring, (ii) early divisome proteins, and (iii) late divisome proteins (1, 2). The successful assembly of the divisome depends on the initial formation of the Z-ring, which is comprised of the 40-kDa bacterial tubulin homologue FtsZ. FtsZ assembles into filaments in a GTP-dependent manner and a headto-tail fashion (3-6). The filaments are then tethered to the membrane, forming the Z-ring. They act as the...

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Novel coiled‐coil cell division factor ZapB stimulates Z ring assembly and cell division

Cited by 118 publications

References 63 publications

FtsZ Ring Stability: of Bundles, Tubules, Crosslinks, and Curves

FtsZ Ring Stability: of Bundles, Tubules, Crosslinks, and Curves

In the Beginning, Escherichia coli Assembled the Proto-ring: An Initial Phase of Division

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

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