Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.
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http://dx.doi.org/10.1021/acs.jpcb.8b00663 | DOI Listing |
Cell Tissue Res
December 2024
Unit of Evolutionary Biology/Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, 14476, Potsdam, Germany.
The adult electric organ in weakly electric mormyrid fish consists of action-potential-generating electrocytes, structurally and functionally modified skeletal muscle cells. The electrocytes have a disc-shaped portion and, on one of its sides, numerous thin processes, termed stalklets. These unite to stalks leading to a single main stalk that carries the innervation site.
View Article and Find Full Text PDFRes Sq
December 2024
Department of Biology, Indiana University, Indianapolis, IN.
In the auditory and vestibular systems, stereocilia are actin-based protrusions that convert mechanical stimuli into electrical signals. During development, stereocilia elongate and widen by adding filamentous actin (F-actin), attaining their mature shape necessary for mechanosensitive function. Myosin motors, including MYO3A/B and MYO15A, are required for normal stereocilia growth, but the regulation of actin and the impact of myosins on actin assembly remain unclear.
View Article and Find Full Text PDFNat Phys
October 2024
Dept. of Chemical Engineering, Stanford University, Palo Alto, CA USA.
During host infection, and related unicellular parasites move using gliding, which differs fundamentally from other known mechanisms of eukaryotic cell motility. Gliding is thought to be powered by a thin layer of flowing filamentous (F)-actin sandwiched between the plasma membrane and a myosin-covered inner membrane complex. How this surface actin layer drives the various gliding modes observed in experiments-helical, circular, twirling and patch, pendulum or rolling-is unclear.
View Article and Find Full Text PDFPLoS Comput Biol
December 2024
Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
Small GTPases of the Rho family play a central role in the regulation of cell motility by controlling the remodeling of the actin cytoskeleton. In the amoeboid cells of Dictyostelium discoideum, the active form of the Rho GTPase Rac1 regulates actin polymerases at the leading edge and actin filament bundling proteins at the posterior cortex of polarized cells. We monitored the spatiotemporal dynamics of Rac1 and its effector DGAP1 in vegetative amoebae using specific fluorescent probes.
View Article and Find Full Text PDFPhys Rev Lett
November 2024
Department of Physics, Yale University, 217 Prospect Street, New Haven, Connecticut 06511, USA.
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