Direct measurement of stiffness of single actin filaments with and without tropomyosin by in vitro nanomanipulation

H. Kojima, A. Ishijima, T. Yanagida

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384 Citations (Scopus)

Abstract

In order to explain the molecular mechanism of muscle contraction, it is crucial to know the distribution of the sarcomere compliance of active muscle. Here, we directly measure the stiffness of single actin filaments with and without tropomyosin, using a recently developed technique for nanomanipulation of single actin filaments with microneedles. The results show that the stiffness for 1-μm-long actin filaments with and without tropomyosin is 65.3 ± 6.3 and 43.7 ± 4.6 pN/nm, respectively. When the distribution of crossbridge forces along the actin filament is taken into account, the elongation of a 1-μm-long thin filament during development of isometric contraction is calculated to be ≃0.23%. The time constant of force in response to a sudden length change is <0.2 ms, indicating that the viscoelasticity is negligible in the millisecond time range. These results suggest that ≃50% of the sarcomere compliance of active muscle is due to extensibility of the thin filaments.

Original languageEnglish
Pages (from-to)12962-12966
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number26
DOIs
Publication statusPublished - 1994 Dec 20

ASJC Scopus subject areas

  • General

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