F-actin-heavy meromyosin complex studied by optical homodyne and heterodyne methods

Satoru Fujime, Shin'ichi Ishiwata, Tadakazu Maeda

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Quasi-elastic scattering of laser light is now becoming a powerful tool for the study of dynamic properties of both biological and non-biological macromolecules. In solutions of biological macromolecules, aggregation-disaggregation of molecules under study usually depends on solvent conditions. Therefore, special attention must be paid in light-beating spectroscopy. By use of both homodyne and heterodyne methods, the spectral densities of solutions of F-actin and of a complex of F-actin and heavy meromyosin were measured. The half-width of the heterodyne spectrum was much wider than that of the homodyne spectrum. This was probably due to polydispersity of F-actin. The results showed that laser light scattering gave information about the dynamics of free filaments, although low frequency rheometry has suggested the rubber-like elasticity of the solution of F-actin and heavy meromyosin. The interaction between F-actin and heavy meromyosin was studied in the presence of pyrophosphate (PPi). At PPi concentrations between 10 and 100 μM, the spontaneous bending motion of F-actin occurred as if heavy meromyosin were not present, although turbidity of the solution indicated that heavy meromyosin was, in fact, bound to F-actin. This meant that there were two types of binding state of the F-actin-heavy meromyosin complex. A plausible model is that, in the absence of PPi, the two heads of one heavy meromyosin molecule simultaneously interact with two neighbouring monomers in F-actin, whereas a single head binding occurs in the presence of PPi. Above 100 μM PPi, heavy meromyosin seemed to dissociate from F-actin. However, it was not clear whether or not this was due to a direct effect of PPi on heavy meromyosin alone, because the dynamic properties of F-actin also changed. Assuming that actin filaments are cross-linked by myosin, a simple model is proposed to explain qualitatively the rubber-like elasticity of the solution of an F-actin-heavy meromyosin complex.

Original languageEnglish
Pages (from-to)351-363
Number of pages13
JournalBBA - Bioenergetics
Volume283
Issue number2
DOIs
Publication statusPublished - 1972 Nov 17
Externally publishedYes

Fingerprint

Myosin Subfragments
Actins
Rubber
Elasticity
Macromolecules
Lasers
Light
Molecules
Elastic scattering
Spectral density
Myosins
Polydispersity
Actin Cytoskeleton
Turbidity
Light scattering
Spectrum Analysis

ASJC Scopus subject areas

  • Biophysics
  • Medicine(all)

Cite this

F-actin-heavy meromyosin complex studied by optical homodyne and heterodyne methods. / Fujime, Satoru; Ishiwata, Shin'ichi; Maeda, Tadakazu.

In: BBA - Bioenergetics, Vol. 283, No. 2, 17.11.1972, p. 351-363.

Research output: Contribution to journalArticle

Fujime, Satoru ; Ishiwata, Shin'ichi ; Maeda, Tadakazu. / F-actin-heavy meromyosin complex studied by optical homodyne and heterodyne methods. In: BBA - Bioenergetics. 1972 ; Vol. 283, No. 2. pp. 351-363.
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