The Bacterial Actin-Like Cytoskeleton

Carballido-López, Rut

doi:10.1128/mmbr.00014-06

Cited by 177 publications

(74 citation statements)

References 181 publications

(311 reference statements)

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“…Although the cell biology of MreB has developed at a rapid pace (12), our understanding of MreB at the biochemical level is currently lacking. Low cellular abundance and difficulty in overexpression and purification have thus far precluded biochemical characterization of the molecule in native form (9,10).…”

mentioning

confidence: 99%

Polymerization Properties of theThermotoga maritimaActin MreB: Roles of Temperature, Nucleotides, and Ions

2007

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MreB is a bacterial ortholog of actin that affects cell shape, polarity and chromosome segregation. Although a significant body of work has explored its cellular functions, we know very little about the biochemical behavior of MreB. We have cloned, overexpressed in E. coli, and purified untagged MreB1 from Thermotoga maritima. We have characterized the conditions that regulate its monomerto-polymer assembly reaction, the critical concentrations of that reaction, the manner in which MreB uses nucleotides, its stability, and the structure of the assembled polymer. MreB requires a bound purine nucleotide for polymerization and rapidly hydrolyzes it following assembly. MreB assembly contains two distinct components, one that does not require divalent cations and one that does, which may comprise the nucleation and elongation phases of assembly, respectively. MreB assembly is strongly favored by increasing temperature or protein concentration but inhibited differentially by high concentrations of monovalent salts. Polymerization rate increases and bulk critical concentration decreases with increasing temperature, but in contrast to previous reports, MreB is capable of polymerizing across a broad range of temperatures. MreB polymers are shorter, stiffer, and scatter more light than eukaryotic actin filaments. Due to rapid ATP hydrolysis and phosphate release, we suggest that most assembled MreB in cells is in the ADP-bound state. Because of only moderate differences between the ATP and ADP critical concentrations, treadmilling may occur, but we do not predict dynamic instability in cells. Because of the relatively low cellular concentration of MreB and the observed structural properties of the polymer, a single MreB assembly may exist in cells.The untested assumption that bacteria lack a cytoskeleton (1) was overturned by the discoveries of prokaryotic orthologs (2,3) of tubulin (4), actin (5,6), and even intermediate filament proteins (7). The tubulin ortholog FtsZ drives contraction of the septum during cytokinesis; the intermediate filament ortholog crescentin causes the distinctive, eponymous shape of Caulobacter crescentus; and the actin ortholog MreB drives the establishment or maintenance of cell shape in all asymmetrical eubacteria yet studied (8). Although the primary structure of MreB is poorly conserved with respect to eukaryotic actins, MreB shares a nearly superimposable tertiary structure with the eukaryotic actin monomer (6) and can assemble into polymers in vitro (6,9,10) and in cells (5,11).Although the cell biology of MreB has developed at a rapid pace (12), our understanding of MreB at the biochemical level is currently lacking. Low cellular abundance and difficulty in overexpression and purification have thus far precluded biochemical characterization of the (9,10). Nonetheless, six decades of work on the eukaryotic actin cytoskeleton has taught us that the cell biology of the system can not be understood without a rigorous, quantitative understanding of the molecules and interactions that...

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confidence: 99%

Polymerization Properties of theThermotoga maritimaActin MreB: Roles of Temperature, Nucleotides, and Ions

2007

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“…As already mentioned, mreB could have a role in A-motility. It is actually not surprising that mreB was not found in motility screens because it is likely an essential gene as in other bacteria [40]. However, as bacteria contain several actin-like and non-actin-like filaments, other filaments might be involved [41].…”

Section: Predictions and Future Perspectivesmentioning

confidence: 98%

The elusive engine in Myxococcus xanthus gliding motility

Mignot

2007

Cell. Mol. Life Sci.

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Bacterial motility is essential for chemotaxis, virulence and complex social interactions leading to biofilm and fruiting body formation. Although bacterial swimming in liquids with a flagellum is well understood, little is known regarding bacterial movements across solid surfaces. Gliding motility, one such mode of locomotion, has remained largely mysterious because cells move smoothly along their long axis in the absence of any visible organelle. In this review, I discuss recent evidence that focal adhesion systems mediate gliding motility in the social bacterium Myxococcus xanthus and combine this evidence with previous work to suggest a new working hypothesis inspired from knowledge in apicomplexan parasites. I then propose experimental directions to test the model and compare it to other pre-existing models. Finally, evidence on gliding mechanisms of selected organisms are presented to ask whether some features of the model have precedents in other bacteria and whether this complex biological process could be explained by a single mechanism or involves multiple distinct mechanisms.

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The helices may arise from the intrinsic curvature of the filament. 1,2 Such a filament may form a free standing helix, and maintain the helical configuration under uniaxial tip force either in free space or under confinement.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7][8][9][10] MreB and MreB homologs are found in all rod-shaped bacteria, 5,9,10 and play important roles in lots of cellular functions, including the regulation of cell shape, chromosome segregation, determination of cell polarity, and organization of membranous organelles. 3,6,9,10 For instance, MreB is essential for the maintenance of a rod-like cell shape, as their disruption leads to cell rounding. MreB and its relatives are actin homolog proteins which are intrinsically straight, i.e., when they are free of external force and torque, their ground state configuration is a straight line.…”

Section: Introductionmentioning

confidence: 99%

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Stability of the helical configuration of an intrinsically straight semiflexible biopolymer inside a cylindrical cell

Zhou

Joós

2017

AIP Advances

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We examine the effects of the external force, torque, temperature, confinement, and excluded volume interactions (EVIs) on the stability of the helical configuration of an intrinsically straight semiflexible biopolymer inside a cylindrical cell. We find that to stabilize a helix, the confinement from both ends of the cell is more effective than a uniaxial force. We show that under a uniaxial force and in absence of confinement from bottom of the cell, a stable helix is very short. Our results reveal that to maintain a low pitch helix, a torque acting at both ends of the filament is a necessity, and the confinement can reduce the required torque to less than half making it much easier to form a stable helix. Moreover, we find that thermal fluctuations and EVIs have little impact on the stability of a helix. Our results can help understand the existence of the helix and ring configurations of some semiflexible biopolymers, such as MreB homologs, inside a rod-shaped bacteria.

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The Bacterial Actin-Like Cytoskeleton

Cited by 177 publications

References 181 publications

Polymerization Properties of theThermotoga maritimaActin MreB: Roles of Temperature, Nucleotides, and Ions

Polymerization Properties of theThermotoga maritimaActin MreB: Roles of Temperature, Nucleotides, and Ions

The elusive engine in Myxococcus xanthus gliding motility

Stability of the helical configuration of an intrinsically straight semiflexible biopolymer inside a cylindrical cell

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