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Updated: Jul 14, 2026

Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Load-dependent mechanism of nonmuscle myosin 2
Mihály Kovács1, Kavitha Thirumurugan, Peter J Knight
1Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute/NIH, Bethesda, MD 20892-8015, USA. kovacsm@elte.hu
Abstract:
Loads on molecular motors regulate and coordinate their function. In a study that directly measures properties of internally strained myosin 2 heads bound to actin, we find that human nonmuscle myosins 2A and 2B show marked load-dependent changes in kinetics of ADP release but not in nucleotide binding. We show that the ADP release rate constant is increased 4-fold by the assisting load on one head and decreased 5-fold (for 2A) or 12-fold (for 2B) by the resisting load on the other. Thus these myosins, especially 2B, have marked mechanosensitivity of product release. By regulating the actin attachment of myosin heads, this provides a basis for energy-efficient tension maintenance without obstructing cellular contractility driven by other motors such as smooth muscle myosin. Whereas forward load accelerates the cycle of interaction with actin, resistive load increases duty ratio to favor tension maintenance by two-headed attachment.
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