title: Sensitivity of small myosin II ensembles from different isoforms to mechanical load and ATP concentration.
abstract: Based on a detailed crossbridge model for individual myosin II motors, we systematically study the influence of mechanical load and adenosine triphosphate (ATP) concentration on small myosin II ensembles made from different isoforms. For skeletal and smooth muscle myosin II, which are often used in actomyosin gels that reconstitute cell contractility, fast forward movement is restricted to a small region of phase space with low mechanical load and high ATP concentration, which is also characterized by frequent ensemble detachment. At high load, these ensembles are stalled or move backwards, but forward motion can be restored by decreasing ATP concentration. In contrast, small ensembles of nonmuscle myosin II isoforms, which are found in the cytoskeleton of nonmuscle cells, are hardly affected by ATP concentration due to the slow kinetics of the bound states. For all isoforms, the thermodynamic efficiency of ensemble movement increases with decreasing ATP concentration, but this effect is weaker for the nonmuscle myosin II isoforms.
authors.affiliation: Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Erdmann
authors.affiliation: Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Bartelheimer
authors.affiliation: Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany.
authors.forename: Ulrich S
authors.initials: US
authors.lastname: Schwarz
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D001696:Biomechanical Phenomena; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects*; D024462:Myosin Type II / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D000255:Adenosine Triphosphate; D024462:Myosin Type II