In vivo myosin step-size from zebrafish skeletal muscle

Open Biol. 2016 May;6(5):160075. doi: 10.1098/rsob.160075. Epub 2016 May 25.


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.

Keywords: highly inclined thin illumination; single myosin detection in vivo; strychnine induced contraction; transgenic zebrafish skeletal muscle; zebrafish skeletal myosin powerstroke; zebrafish skeletal myosin step-size.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Animals, Genetically Modified
  • Binding Sites
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / embryology*
  • Muscle, Skeletal / metabolism
  • Myosin Light Chains / chemistry*
  • Myosin Light Chains / genetics
  • Myosin Light Chains / metabolism*
  • Strychnine / pharmacology
  • Zebrafish / embryology
  • Zebrafish / genetics*


  • Actins
  • Myosin Light Chains
  • Green Fluorescent Proteins
  • Adenosine Triphosphate
  • Strychnine