Abstract of my talk “Coordinated Dynamics of 10 to 100 Mechanically Coupled Molecular Motors.” (Invited Speaker, SFB 937 “Collective behavior of soft and biological matter”, University Göttingen, May 12th, 2015)

Individual proteins converting chemical energy into force and motion, so called “molecular motors”, drive various mechanical processes in biology. Individual molecular motors work in discrete steps and show the stochasticity that is typical of single molecule reactions. In most cases, however, several motors work on a shared target or cargo. Effectively, these motors are mechanically coupled and distinct group dynamics emerge in many cases.

I will review our work for 10 up to 100 coupled molecular motors. In our experiments (in vitro motility assay), passive actin filaments of constant length are moved by a stationary, two-dimensional layer of muscle myosin motors. We developed new video analysis software to extract the distribution of actin sliding velocities for different actin lengths [1]. Like this, we can measure how actin sliding changes as 10 up to 100 myosins are allowed to simultaneously work on a shared actin filament. We also built a mechanistic mathematical model, which follows all individual myosins [2]. Myosin stepping rates are assumed to increase or decrease, dependent on the mechanical work difference a given step would affect to the elastic network of all simultaneously bound myosin motors. In the experiment as well as the simulation, actin motion is clearly separated into phases of full arrest vs. phases of sliding with a stable velocity [2,3].

I will introduce our microscopic explanation of this macroscopic stop-and-go behavior. I will also present recent insights how chemical and mechanical perturbations affect actin sliding dynamics [3,4].

[1] Hilbert et al. PLoS Comp Biol 2013
[2] Hilbert et al. Biophys J 2013
[3] Hilbert et al. Biophys J 2015
[4] Unpublished work

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