Quasiperiodic distribution of rigor cross-bridges along a reconstituted thin filament in a skeletal myofibril

Madoka Suzuki, Shin'Ichi Ishiwata

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Electron microscopy has shown that cross-bridges (CBs) are formed at the target zone that is periodically distributed on the thin filament in striated muscle. Here, by manipulating a single bead-tailed actin filament with optical tweezers, we measured the unbinding events of rigor CBs one by one on the surface of the A-band in rabbit skeletal myofibrils. We found that the spacings between adjacent CBs were not always the same, and instead were 36, 72, or 108 nm. Tropomyosin and troponin did not affect the CB spacing except for a relative increase in the appearance of longer spacing in the presence of Ca 2+. In addition, in an in vitro assay where myosin molecules were randomly distributed, were obtained the same spacing, i.e., a multiple of 36 nm. These results indicate that the one-dimensional distribution of CBs matches with the 36-nm half pitch of a long helical structure of actin filaments. A stereospecific model composed of three actin protomers per target zone was shown to explain the experimental results. Additionally, the unbinding force (i.e., the binding affinity) of CBs for the reconstituted thin filaments was found to be larger and smaller relative to that for actin filaments with and without Ca 2+, respectively.

Original languageEnglish
Pages (from-to)2740-2748
Number of pages9
JournalBiophysical Journal
Volume101
Issue number11
DOIs
Publication statusPublished - 2011 Dec 7

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Myofibrils
Actin Cytoskeleton
Optical Tweezers
Tropomyosin
Troponin
Striated Muscle
Protein Subunits
Myosins
Actins
Electron Microscopy
Rabbits

ASJC Scopus subject areas

  • Biophysics

Cite this

Quasiperiodic distribution of rigor cross-bridges along a reconstituted thin filament in a skeletal myofibril. / Suzuki, Madoka; Ishiwata, Shin'Ichi.

In: Biophysical Journal, Vol. 101, No. 11, 07.12.2011, p. 2740-2748.

Research output: Contribution to journalArticle

Suzuki, Madoka ; Ishiwata, Shin'Ichi. / Quasiperiodic distribution of rigor cross-bridges along a reconstituted thin filament in a skeletal myofibril. In: Biophysical Journal. 2011 ; Vol. 101, No. 11. pp. 2740-2748.
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