Delayed dissociation of in vitro moving actin filaments from heavy meromyosin induced by low concentrations of Triton X-100

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Abstract

The in vitro motility of fluorescent actin filaments over heavy meromyosin (HMM) was studied in the presence of the nonionic detergent Triton X-100. Below 0.004% Triton X-100 concentration, motility was not affected. Above 0.007%, motility was not observed because actin filaments were dissociated from HMM. In the Triton X-100 concentration range of 0.004- 0.007%, the sliding actin filaments dissociated from HMM with a delay. The dissociation delay time decreased with increasing Triton X-100 concentration, increasing ATP (adenosine-5'-triphosphate) concentration, and increasing temperature. The delayed acto-HMM dissociation was absent when weak-binding kinetic intermediates of the myosin ATPase cycle (M.ATP and M.ADP-P(i)) were used. The presence of sliding movement was necessary to evoke the delayed acto-HMM dissociation. The acto-HMM dissociation delay was independent of actin filament length. For a given Triton X-100 concentration, the dissociation delay time was found to be inversely proportional to sliding velocity, indicating that actin filaments travel a more or less constant distance prior to dissociation from HMM. The actin-activated HMM ATPase activity was not inhibited by Triton X-100; rather, it was slightly enhanced. The results imply the presence of a motility-associated conformational change in acto-HMM.

Original languageEnglish
Pages (from-to)199-210
Number of pages12
JournalBiophysical Chemistry
Volume67
Issue number1-3
DOIs
Publication statusPublished - Sep 1 1997

Keywords

  • ATPase
  • Chemomechanical transduction
  • In vitro motility
  • Muscle contraction
  • Nonionic detergent

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Organic Chemistry

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