The Structure and Function of Bacterial Actin Homologs

Shaevitz, Joshua W.; Gitai, Zemer

doi:10.1101/cshperspect.a000364

Cited by 79 publications

(72 citation statements)

References 94 publications

(143 reference statements)

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“…The deletion of MreB, or the inhibition of MreB polymerization using the drug A22, leads to spherical cells that are prone to lysis and have an altered cell wall structure (5,8,9). During elongation, we observed that MreB has a preference to localize to regions of small or even negative local Gaussian curvature.…”

Section: Introductionmentioning

confidence: 87%

MreB Orientation Correlates with Cell Diameter in Escherichia coli

Ouzounov

Nguyen

Bratton

et al. 2016

Biophysical Journal

127

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Bacteria have remarkably robust cell shape control mechanisms. For example, cell diameter only varies by a few percent across a given population. The bacterial actin homolog, MreB, is necessary for establishment and maintenance of rod shape although the detailed properties of MreB that are important for shape control remained unknown. In this study, we perturb MreB in two ways: by treating cells with the polymerization-inhibiting drug A22 and by creating point mutants in mreB. These perturbations modify the steady-state diameter of cells over a wide range, from 790 5 30 nm to 1700 5 20 nm. To determine which properties of MreB are important for diameter control, we correlated structural characteristics of fluorescently tagged MreB polymers with cell diameter by simultaneously analyzing three-dimensional images of MreB and cell shape. Our results indicate that the helical pitch angle of MreB inversely correlates with the cell diameter of Escherichia coli. Other correlations between MreB and cell diameter are not found to be significant. These results demonstrate that the physical properties of MreB filaments are important for shape control and support a model in which MreB organizes the cell wall growth machinery to produce a chiral cell wall structure and dictate cell diameter.

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Section: Introductionmentioning

confidence: 87%

MreB Orientation Correlates with Cell Diameter in Escherichia coli

Ouzounov

Nguyen

Bratton

et al. 2016

Biophysical Journal

127

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show abstract

“…Of the bacterial cytoskeletal proteins, the widely conserved actin homolog MreB is particularly important for bacterial cells to elongate and maintain a rod-like shape. MreB forms polymers that are associated with the cell membrane and distributed along the length of the cell in many rod-shaped bacteria (2). These polymeric MreB structures are essential for the maintenance of rod-like cell shape, as their disruption leads to cell rounding.…”

mentioning

confidence: 99%

The bacterial actin MreB rotates, and rotation depends on cell-wall assembly

Teeffelen

Wang

Furchtgott

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

385

398

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Bacterial cells possess multiple cytoskeletal proteins involved in a wide range of cellular processes. These cytoskeletal proteins are dynamic, but the driving forces and cellular functions of these dynamics remain poorly understood. Eukaryotic cytoskeletal dynamics are often driven by motor proteins, but in bacteria no motors that drive cytoskeletal motion have been identified to date. Here, we quantitatively study the dynamics of the Escherichia coli actin homolog MreB, which is essential for the maintenance of rod-like cell shape in bacteria. We find that MreB rotates around the long axis of the cell in a persistent manner. Whereas previous studies have suggested that MreB dynamics are driven by its own polymerization, we show that MreB rotation does not depend on its own polymerization but rather requires the assembly of the peptidoglycan cell wall. The cell-wall synthesis machinery thus either constitutes a novel type of extracellular motor that exerts force on cytoplasmic MreB, or is indirectly required for an as-yetunidentified motor. Biophysical simulations suggest that one function of MreB rotation is to ensure a uniform distribution of new peptidoglycan insertion sites, a necessary condition to maintain rod shape during growth. These findings both broaden the view of cytoskeletal motors and deepen our understanding of the physical basis of bacterial morphogenesis.bacterial cytoskeletal dynamics | cell-wall organization | peptidoglycan synthesis | cell growth C ytoskeletal proteins play an important role in bacterial morphogenesis (1). Of the bacterial cytoskeletal proteins, the widely conserved actin homolog MreB is particularly important for bacterial cells to elongate and maintain a rod-like shape. MreB forms polymers that are associated with the cell membrane and distributed along the length of the cell in many rod-shaped bacteria (2). These polymeric MreB structures are essential for the maintenance of rod-like cell shape, as their disruption leads to cell rounding. Although MreB is essential for proper morphogenesis, bacterial cell shape is ultimately determined by the shape of the peptidoglycan cell-wall sacculus, which in turn is controlled by the cell-wall synthesis machinery. The cell wall, which is composed of stiff glycan strands cross-linked by flexible peptide linkers, forms a load-bearing structure that can counteract the intracellular turgor pressure. Cell-wall assembly requires peptidoglycan subunits to be synthesized, polymerized into glycan strands by transglycosylase enzymes, and cross-linked into the existing cell-wall network by transpeptidase enzymes. MreB directly or indirectly associates with a number of proteins that have been implicated in cell-wall assembly, such that MreB is believed to act upstream of the cell-wall assembly machinery to direct the synthesis enzymes to the sites of cell-wall insertion.Previous studies have demonstrated that MreB structures are dynamic in Bacillus subtilis and Caulobacter crescentus (3-7). To date, no motor proteins have been shown to either ...

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“…There are, in contrast, at least 30 distinct families of Alps that are encoded on a variety of mobile genetic elements, and many of these Alps perform the same function. For example, Alp7A, AlfA, and ParM represent three distantly related families of Alps; they are encoded on three different plasmids, yet they all segregate plasmids (1,4,27,32,47). Their identical function notwithstanding, these Alps have been shown to differ in their cell biological and in their biophysical properties (1,4,10,11,26,32).…”

mentioning

confidence: 99%

“…There is regulation of actin function and activity in other actin-based plasmid segregation systems, but it can be of a very different sort. In the parMR operon of the Escherichia coli plasmid R1, for example, the parM gene codes for another bacterial actin that is distantly related to eukaryotic actin, to the alp7 family, and to the other bacterial actin families (4,12,13,45,47). ParM, like Alp7A, is a plasmid segregation determinant, and filaments of both this prototypical ParM and the ParM of plasmid pB171 exhibit dynamic instability (10,11,34,37,41).…”

mentioning

confidence: 99%

“…The Alps are themselves evolutionarily diverse and so, in order to lay the groundwork for understanding this diversity, we have organized them into families whose members show at least 30% amino acid identity (4,47). Although only a small number of Alp families have been studied to date, it has become apparent that the Alps share the basic properties of eukaryotic actin.…”

mentioning

confidence: 99%

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