Phalloidin affects the myosin-dependent sliding velocities of actin filaments in a bound-divalent cation dependent manner

Kiyotaka Tokuraku, Taro Q.P. Uyeda

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

We examined sliding velocities in vitro of four types of actin filaments, that is, filaments with Ca 2+ or Mg 2+ bound at the high affinity metal binding site, each with rhodamine phalloidin bound with a high or low stoichiometry. When surfaces coated with a high density of heavy meromyosin (HMM) were used, high stoichiometric concentrations of rhodamine phalloidin reduced sliding velocities of only Ca 2+-actin filaments, by 40%. As the HMM density on surfaces was reduced, continuous movement of actin filaments became dependent on the presence of methylcellulose and sliding velocities of all four types became progressively slower. Interestingly, Ca 2+-actin filaments with a high stoichiometric concentration of rhodamine phalloidin were the fastest among the four types of filaments on sparse HMM surfaces. In contrast, phalloidin did not affect steady state ATPase activities of HMM in the presence of Ca 2+- or Mg 2+-actin filaments. We speculate that the reversal of the order of sliding velocities among the four types of actin filaments between high and low densities of HMM relates with different axial elasticity of the actin filaments, so that stiffer filaments move slower on dense HMM surfaces, but faster on sparse surfaces, than elastic ones.

Original languageEnglish
Pages (from-to)371-378
Number of pages8
JournalJournal of Muscle Research and Cell Motility
Volume22
Issue number4
DOIs
Publication statusPublished - 2001
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Cell Biology

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