Key result
In vivo single myosin detection in zebrafish skeletal muscle revealed that about 17% of active myosin steps fall between 2 and 7 nm, implicating them as powerstrokes.
In vivo single myosin detection in zebrafish skeletal muscle reveals that approximately 17% of active myosin steps are between 2 and 7 nm, representing powerstrokes.
Provides foundational in vivo myosin data from zebrafish; leaves open relevance to human cardiac function.
Muscle myosins transduce ATP free energy into actin displacement to power contraction. In vivo, myosin side chains are modified post-translationally under native conditions, potentially impacting function. Single myosin detection provides the 'bottom-up' myosin characterization probing basic mechanisms without ambiguities inherent to ensemble observation. Macroscopic muscle physiological experimentation provides the definitive 'top-down' phenotype characterizations that are the concerns in translational medicine. In vivo single myosin detection in muscle from zebrafish embryo models for human muscle fulfils ambitions for both bottom-up and top-down experimentation. A photoactivatable green fluorescent protein (GFP)-tagged myosin light chain expressed in transgenic zebrafish skeletal muscle specifically modifies the myosin lever-arm. Strychnine induces the simultaneous contraction of the bilateral tail muscles in a live embryo, causing them to be isometric while active. Highly inclined thin illumination excites the GFP tag of single lever-arms and its super-resolution orientation is measured from an active isometric muscle over a time sequence covering many transduction cycles. Consecutive frame lever-arm angular displacement converts to step-size by its product with the estimated lever-arm length. About 17% of the active myosin steps that fall between 2 and 7 nm are implicated as powerstrokes because they are beyond displacements detected from either relaxed or ATP-depleted (rigor) muscle.
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Burghardt et al. (2016) studied this question. In vivo single myosin detection using GFP-tagging and strychnine vs. Relaxed or ATP-depleted (rigor) muscle was evaluated on Myosin step-size. In vivo single myosin detection in zebrafish skeletal muscle revealed that about 17% of active myosin steps fall between 2 and 7 nm, implicating them as powerstrokes.
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