Conformational changes of F-actin in myosin-free ghost single fibre induced by either phosphorylated or dephosphorylated heavy meromyosin

Irena Kâkol, Yurii S. Borovikov, Danuta Szczêsna, Valentina P. Kirillina, Dimitrii I. Levitsky

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

The changes in F-actin conformation of myosin-free single ghost fibre induced by binding of phosphorylated or dephosphorylated heavy meromyosin have been studied by measuring polarized fluorescence of F-actin intrinsic tryptophan and of phalloidin-rhodamin bound to F-actin. The changes of polarization of both fluorescences were found to be dependent on low or high Ca2+ concenration and on the phosphorylated or dephosphorylated form of heavy meromyosin. Computer analysis of polarized fluorescence has shown that binding of phosphorylated heavy meromyosin with divalent ion binding sites saturated with Mg2+ (in the presence of 1 mM MgCl2 and 1 mM EGTA) and dephosphorylated heavy meromyosin with divalent ion binding sites saturated with Ca2+ (in the presence of 1 mM MgCl2 and 0.1 mM Ca2+) decreases the angles of emission and absorption dipoles and the angle between the F-actin axis and the fibre axis, thus suggesting that F-actin in ghost fibre becomes more flexible. On the other hand, the above-mentioned angles increase when phosphorylated heavy meromyosin at high and dephosphorylated heavy meromyosin at low Ca2+ concentration were bound to thin filaments, thus showing the decrease of F-actin flexibility under these conditions.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume913
Issue number1
DOIs
StatePublished - May 27 1987
Externally publishedYes

Keywords

  • F-actin
  • Fluorescence, polarized
  • Ghost fibre, myosin-free
  • Heavy meromyosin, (de)phosphorylated
  • Myosin

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology
  • Structural Biology

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