Actomyosin interaction at low ATP concentrations

Manuela Maffei, Emanuela Longa, Antonio Sabatini, Alberto Vacca, Stefano Iotti

Research output: Contribution to journalArticlepeer-review


In vitro motility assay (IVMA) experiments were performed to analyze the movement of actin filaments sliding on a pavement of myosin molecules at different [ATP] and [ADP]. In standard experimental conditions at [ATP] = 2 mM, about 80% of the actin filaments move in unloaded conditions with a constant velocity. However, a fraction of at least 20% static actin filaments is always present. The accepted explanation is the occurrence of damaged “rigor”-like myosin heads that do not undergo the normal ATP-dependent cycling motion. However, in a series of IVMA experiments performed at different [ATP] we observed that the mobility of actin filaments increased with lowering [ATP]. We investigated the influence of [ATP] on the number of mobile actin filaments. IVMA experiments were performed at controlled nucleotide concentrations and the percentage of mobile filaments accurately determined by specific operator-guided software. The value of ΔGATP involved was determined. Results showed that the number of mobile actin filaments sliding on type 2B heavy meromyosin isoform (2B HMM) increased at very low [ATP] accompanied by less negative ΔGATP values. Similar results were obtained by increasing [ADP]. Performing experiments at the same [ATP] with different myosin types, we found a higher number of mobile actin filaments on slow type 1 HMM with respect to type 2B HMM while the highest number of mobile actin filaments was found on single-head myosin (S1 fraction). We also found that [ATP] did not influence the percentage of mobile actin filaments sliding on S1. Our results reveal novel aspects of actomyosin interaction.

Original languageEnglish
Pages (from-to)195-202
Number of pages8
JournalEuropean Biophysics Journal
Issue number2
Publication statusPublished - Mar 1 2017
Externally publishedYes


  • Actomyosin interaction
  • ATP concentration
  • ATP hydrolysis
  • Gibbs free energy
  • In vitro motility assay

ASJC Scopus subject areas

  • Biophysics


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