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  • 1
    Electronic Resource
    Electronic Resource
    New wrinkles in cytokinesis (1997)
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 388-389 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Once in every cell cycle, the mother cell splits itself into two daughters, each of which receives its fair share of the mother's contents. To do this, not only must the chromosomes be replicated and split with perfect precision by the mitotic spindle (Fig. 1), but all of the other cell contents - ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/385388a0
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  • 2
    Electronic Resource
    Electronic Resource
    CRAWLING TOWARD A UNIFIED MODEL OF CELL MOBILITY: Spatial and Temporal Regulation of Actin Dynamics (2004)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 73 (2004), S. 209-239 
    Details
    ISSN: 0066-4154
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Biology
    Notes: Crawling cells of various morphologies displace themselves in their biological environments by a similar overall mechanism of protrusion through actin assembly at the front coordinated with retraction at the rear. Different cell types organize very distinct protruding structures, yet they do so through conserved biochemical mechanisms to regulate actin polymerization dynamics and vary the mechanical properties of these structures. The moving cell must spatially and temporally regulate the biochemical interactions of its protein components to exert control over higher-order dynamic structures created by these proteins and global cellular responses four or more orders of magnitude larger in scale and longer in time than the individual protein-protein interactions that comprise them. To fulfill its biological role, a cell globally responds with high sensitivity to a local perturbation or signal and coordinates its many intracellular actin-based functional structures with the physical environment it experiences to produce directed movement. This review attempts to codify some unifying principles for cell motility that span organizational scales from single protein polymer filaments to whole crawling cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.biochem.73.011303.073844
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  • 3
    Electronic Resource
    Electronic Resource
    CRAWLING TOWARD A UNIFIED MODEL OF CELL MOTILITY: Spatial and Temporal Regulation of Actin Dynamics (2004)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 73 (2004), S. 209-239 
    Details
    ISSN: 0066-4154
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Biology
    Notes: Crawling cells of various morphologies displace themselves in their biological environments by a similar overall mechanism of protrusion through actin assembly at the front coordinated with retraction at the rear. Different cell types organize very distinct protruding structures, yet they do so through conserved biochemical mechanisms to regulate actin polymerization dynamics and vary the mechanical properties of these structures. The moving cell must spatially and temporally regulate the biochemical interactions of its protein components to exert control over higher-order dynamic structures created by these proteins and global cellular responses four or more orders of magnitude larger in scale and longer in time than the individual protein-protein interactions that comprise them. To fulfill its biological role, a cell globally responds with high sensitivity to a local perturbation or signal and coordinates its many intracellular actin-based functional structures with the physical environment it experiences to produce directed movement. This review attempts to codify some unifying principles for cell motility that span organizational scales from single protein polymer filaments to whole crawling cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.biochem.73.011303.073844
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  • 4
    Electronic Resource
    Electronic Resource
    Ena/VASP proteins contribute to Listeria monocytogenes pathogenesis by controlling temporal and spatial persistence of bacterial actin-based motility (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Listeria monocytogenes surface protein ActA mediates actin-based motility by interacting with a number of host cytoskeletal components, including Ena/VASP family proteins, which in turn interact with actin and the actin-binding protein profilin. We employed a bidirectional genetic approach to study Ena/VASP′s contribution to L. monocytogenes movement and pathogenesis. We generated an ActA allelic series within the defined Ena/VASP-binding sites and introduced the resulting mutant L. monocytogenes into cell lines expressing different Ena/VASP derivatives. Our findings indicate that Ena/VASP proteins contribute to the persistence of both speed and directionality of L. monocytogenes movement. In the absence of the Ena/VASP proline-rich central domain, speed consistency decreased by sixfold. In addition, the   Ena/VASP   F-actin-binding   region   increased directionality     of     bacterial     movement     by     fourfold. We further show that both regions of Ena/VASP enhanced L. monocytogenes cell-to-cell spread to a similar degree, although the Ena/VASP F-actin-binding region did so in an ActA-independent manner. Surprisingly, our ActA allelic series enabled us to uncouple L. monocytogenes speed from directionality although both were controlled by Ena/VASP proteins. Lastly, we showed the pathogenic relevance of these findings by the observation that L. monocytogenes lacking   ActA   Ena/VASP-binding   sites   were   up   to 400-fold less virulent during an adaptive immune response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03639.x
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  • 5
    Electronic Resource
    Electronic Resource
    Systematic mutational analysis of the amino-terminal domain of the Listeria monocytogenes ActA protein reveals novel functions in actin-based motility (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Listeria monocytogenes ActA protein acts as a scaffold to assemble and activate host cell actin cytoskeletal factors at the bacterial surface, resulting in directional actin polymerization and propulsion of the bacterium through the cytoplasm. We have constructed 20 clustered charged-to-alanine mutations in the NH2-terminal domain of ActA and replaced the endogenous actA gene with these molecular variants. These 20 clones were evaluated in several biological assays for phenotypes associated with particular amino acid changes. Additionally, each protein variant was purified and tested for stimulation of the Arp2/3 complex, and a subset was tested for actin monomer binding. These specific mutations refined the two regions involved in Arp2/3 activation and suggest that the actin-binding sequence of ActA spans 40 amino acids. We also identified a ‘motility rate and cloud-to-tail transition’ region in which nine contiguous mutations spanning amino acids 165–260 caused motility rate defects and changed the ratio of intracellular bacteria associated with actin clouds and comet tails without affecting Arp2/3 activation. Several unusual motility phenotypes were associated with amino acid changes in this region, including altered paths through the cytoplasm, discontinuous actin tails in host cells and the tendency to ‘skid’ or dramatically change direction while moving. These unusual phenotypes illustrate the complexity of ActA functions that control the actin-based motility of L. monocytogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02677.x
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  • 6
    Electronic Resource
    Electronic Resource
    Complex spatial distribution and dynamics of an abundant Escherichia coli outer membrane protein, LamB (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Advanced techniques for observing protein localization in live bacteria show that the distributions are dynamic. For technical reasons, most such techniques have not been applied to outer membrane proteins in Gram-negative bacteria. We have developed two novel live-cell imaging techniques to observe the surface distribution of LamB, an abundant integral outer membrane protein in Escherichia coli responsible for maltose uptake and for attachment of bacteriophage lambda. Using fluorescently labelled bacteriophage lambda tails, we quantitatively des-cribed the spatial distribution and dynamic movement of LamB in the outer membrane. LamB accumulated in spiral patterns. The distribution depended on cell length and changed rapidly. The majority of the protein diffused along spirals extending across the cell body. Tracking single particles, we found that there are two populations of LamB – one shows very restricted diffusion and the other shows greater mobility. The presence of two populations recalls the partitioning of eukaryotic membrane proteins between ‘mobile’ and ‘immobile’ populations. In this study, we have demonstrated that LamB moves along the bacterial surface and that these movements are restricted by an underlying dynamic spiral pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04242.x
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  • 7
    Electronic Resource
    Electronic Resource
    The making of a gradient: IcsA (VirG) polarity in Shigella flexneri (2001)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 41 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The generation and maintenance of subcellular organization in bacteria is critical for many cell processes and properties, including growth, structural integrity and, in pathogens, virulence. Here, we investigate the mechanisms by which the virulence protein IcsA (VirG) is distributed on the bacterial surface to promote efficient transmission of the bacterium Shigella flexneri from one host cell to another. The outer membrane protein IcsA recruits host factors that result in actin filament nucleation and, when concentrated at one bacterial pole, promote unidirectional actin-based motility of the pathogen. We show here that the focused polar gradient of IcsA is generated by its delivery exclusively to one pole followed by lateral diffusion through the outer membrane. The resulting gradient can be modified by altering the composition of the outer membrane either genetically or pharmacologically. The gradient can be reshaped further by the action of the protease IcsP (SopA), whose activity we show to be near uniform on the bacterial surface. Further, we report polar delivery of IcsA in Escherichia coli and Yersinia pseudotuberculosis, suggesting that the mechanism for polar delivery of some outer membrane proteins is conserved across species and that the virulence function of IcsA capitalizes on a more global mechanism for subcellular organization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02552.x
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  • 8
    Electronic Resource
    Electronic Resource
    Asymmetric distribution of the Listeria monocytogenes ActA protein is required and sufficient to direct actin-based motility (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Scientific Publication
    Molecular microbiology 17 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Listeria monocytogenes is a Gram-positive facultative intracytoplasmic bacterial pathogen that exhibits rapid actin-based motility in eukaryotic cells and in cell-free cytoplasmic extracts. The protein product of the actA gene is required for bacterial movement and is normally expressed in a polarized fashion on the bacterial surface. Here we demonstrate that the ActA protein is sufficient to direct motility in the absence of other L. monocytogenes gene products, and that polarized localization of the protein is required for efficient unidirectional movement. We have engineered a fusion protein combining ActA with the C-terminal domain of the LytA protein of Streptococcus pneumoniae, which mediates high-affinity binding to DEAE-cellulose and to choline moieties present in the S. pneumoniae cell wall. DEAE-cellulose fragments or S. pneumoniae coated uniformly with the ActA/LytA fusion protein nucleate actin filament growth in cytoplasmic extracts, but do not move efficiently. However, when ActA/LytA-coated S. pneumoniae is grown to polarize the distribution of the fusion protein, the bacteria exhibit unidirectional actin-based movement similar to the normal movement of L. monocytogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_17050945.x
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  • 9
    Electronic Resource
    Electronic Resource
    Actin microfilament dynamics in locomoting cells (1991)
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 126-131 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The dynamic behaviour of actin filaments has been directly observed in living, motile cells using fluorescence photoactivation. In goldfish epithelial keratocytes, the actin microfilaments in the lamellipodium remain approximately fixed relative to the substrate as the cell moves over them, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/352126a0
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  • 10
    Electronic Resource
    Electronic Resource
    Principles of locomotion for simple-shaped cells (1993)
    [s.l.] : Nature Publishing Group
    Nature 362 (1993), S. 167-171 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The close association between the semicircular shape of keratocytes and their 'gliding' mode of locomotion suggests that cell shape arises from the same process that drives locomotion. The following kinematic description, termed the graded radial ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/362167a0
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