Effect of calcium ions on the flexibility of reconstituted thin filaments of muscle studied by quasielastic scattering of laser light

Shin'ichi Ishiwata, Satoru Fujime

Research output: Contribution to journalArticle

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Abstract

Quasielastic scattering of laser light was used to examine the effect of calcium ions on the flexibility of a reconstituted thin filament, namely, an F-actin/tropomyosin/troponin complex of striated muscle. The results showed that the flexibility of a reconstituted thin filament changed reversibly at about 1 μm of free calcium ions (i.e. the physiological concentration). Below 1 μm-Ca2+ a tropomyosin/troponin system suppressed the bending motion of F-actin. This suppression was removed by calcium ions above 1 μm, and the F-actin flexibility became almost the same as that of an F-actin/tropomyosin complex. A quantitative study showed that calcium ions affected the reconstituted thin filament in two ways at the free calcium ion concentrations of about 1 μm and 20 μm, corresponding, respectively, to the two different calcium binding constants of troponin. An over-all conformational change of a reconstituted thin filament is brought about by calcium ions. It is suggested that the effect of calcium ions on troponin can be transferred to F-actin by altering the binding between tropomyosin and several monomer units in F-actin. The possible role of the dynamic nature of F-actin in muscle contraction is discussed.

Original languageEnglish
Pages (from-to)511-522
Number of pages12
JournalJournal of Molecular Biology
Volume68
Issue number3
DOIs
Publication statusPublished - 1972 Jul 28
Externally publishedYes

Fingerprint

Lasers
Actins
Ions
Calcium
Light
Muscles
Tropomyosin
Troponin
Striated Muscle
Muscle Contraction

ASJC Scopus subject areas

  • Virology

Cite this

Effect of calcium ions on the flexibility of reconstituted thin filaments of muscle studied by quasielastic scattering of laser light. / Ishiwata, Shin'ichi; Fujime, Satoru.

In: Journal of Molecular Biology, Vol. 68, No. 3, 28.07.1972, p. 511-522.

Research output: Contribution to journalArticle

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