Single molecule turnover of fluorescent ATP by myosin and actomyosin unveil elusive enzymatic mechanisms

Commun Biol. 2021 Jan 13;4(1):64. doi: 10.1038/s42003-020-01574-0.

Abstract

Benefits of single molecule studies of biomolecules include the need for minimal amounts of material and the potential to reveal phenomena hidden in ensembles. However, results from recent single molecule studies of fluorescent ATP turnover by myosin are difficult to reconcile with ensemble studies. We found that key reasons are complexities due to dye photophysics and fluorescent contaminants. After eliminating these, through surface cleaning and use of triple state quenchers and redox agents, the distributions of ATP binding dwell times on myosin are best described by 2 to 3 exponential processes, with and without actin, and with and without the inhibitor para-aminoblebbistatin. Two processes are attributable to ATP turnover by myosin and actomyosin respectively, whereas the remaining process (rate constant 0.2-0.5 s-1) is consistent with non-specific ATP binding to myosin, possibly accelerating ATP transport to the active site. Finally, our study of actin-activated myosin ATP turnover without sliding between actin and myosin reveals heterogeneity in the ATP turnover kinetics consistent with models of isometric contraction.

Publication types

  • Research Support, Non-U.S. Gov't
  • Video-Audio Media

MeSH terms

  • Actomyosin / chemistry
  • Actomyosin / metabolism*
  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism*
  • Animals
  • Female
  • Fluorescent Dyes / chemistry
  • Isometric Contraction
  • Microscopy, Fluorescence / methods
  • Myosins / chemistry
  • Myosins / metabolism*
  • Rabbits
  • Single Molecule Imaging / methods
  • Time Factors

Substances

  • Fluorescent Dyes
  • Adenosine Triphosphate
  • Actomyosin
  • Adenosine Triphosphatases
  • Myosins