Regensburg 2013 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 5: Cytoskeleton
BP 5.2: Vortrag
Montag, 11. März 2013, 15:30–15:45, H43
Time dependent irreversible bundling of actin filaments with magnesium ions — Timo Maier1,2, •Tamás Haraszti1,2, and Joachim P. Spatz1,2 — 1New Materials and Biosystems group, MPI for Intelligent Systems, Heisenbergstr. 3, 70569-Stuttgart, Germany — 2Biophysical Chemistry, University of Heidelberg, Im Neuenheimerg Feld 253, 69120-Heidelberg, Germany
Actin, an abundant protein in eukaryotic cells, forms filamentous structures playing critical roles in cellular adhesion, motility and determining the elastic properties and the shape of cells. Mixed with divalent cations, bundles were observed above a critical electrolyte concentration, e.g. 27 mM for Mg2+. The process is driven by counter ion condensation, but there are still unclear details. We have investigated two of these details using 2-dimensional networks of prepolymerized actin filaments, following the bundling process by the thermal motion of tracer particles attached to the bundles and fluorescence microscopy. Our results indicate, that the filaments preferentially adsorb the divalent magnesium ions, resulting in crosslinking down to 5−8 mM background concentration when the solution is provided by a mediate (0.4 µ l/min. loading rate) flow. While the driving forces are in the order of 0.1−0.25 pN, as we have reported earlier in single actin experiments, the resulted bundling is not reversible by thermal motion even after removing the magnesium and adding EGTA to the solution for several hours.