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Updated: Mar 9, 2026
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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
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Actomyosin interaction at low ATP concentrations
Manuela Maffei1, Emanuela Longa2, Antonio Sabatini3
1Department of Molecular Medicine, University of Pavia, Via Forlanini 6, 27100, Pavia, Italy.
European Biophysics Journal : EBJ
|January 1, 2017
Summary
Lowering adenosine triphosphate (ATP) concentration and increasing adenosine diphosphate (ADP) concentration increases actin filament mobility in vitro. This challenges the traditional view of static actin filaments in actomyosin interactions.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Mechanics
Background:
- Actin filament movement on myosin is crucial for cellular functions.
- Traditionally, static actin filaments were attributed to damaged myosin heads.
- Standard in vitro motility assays (IVMA) show ~20% static filaments.
Purpose of the Study:
- To investigate the influence of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentrations on actin filament mobility.
- To re-evaluate the factors contributing to static actin filaments in actomyosin interactions.
- To explore the role of different myosin isoforms in filament motility.
Main Methods:
- In vitro motility assay (IVMA) experiments were conducted at varying ATP and ADP concentrations.
- Operator-guided software was used to quantify the percentage of mobile actin filaments.
- The change in free energy of ATP hydrolysis (ΔG ATP) was calculated.
Main Results:
- Actin filament mobility increased as ATP concentration decreased and ADP concentration increased.
- Higher mobility was observed with less negative ΔG ATP values.
- Different myosin types exhibited varying effects: type 1 HMM showed higher mobility than type 2B HMM, and S1 fraction showed the highest mobility.
Conclusions:
- Nucleotide concentrations, specifically low ATP and high ADP, significantly influence actin filament motility.
- The number of mobile filaments is dependent on the type of myosin isoform.
- Findings suggest a more dynamic regulation of actomyosin interactions than previously assumed.
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