Visualization and force measurement of branching by Arp2/3 complex and N-WASP in actin filament

Ikuko Fujiwara, Shiro Suetsugu, Sotaro Uemura, Tadaomi Takenawa, Shin'ichi Ishiwata*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    46 Citations (Scopus)


    To determine whether the Arp2/3 complex activated by N-WASP (VCA) branches actin filaments at the side (side branching), or at the barbed (B-)end (end branching) of the mother filaments, we have directly observed the branching process of actin filaments and examined single-molecule unbinding under optical microscope. We found that side branching was predominant, though not exclusive. At the initial stage of polymerization, the branching at the B-end occurred and subsequently the side branching started to occur. In either type of branching, the mother and daughter filaments elongated at nearly the same rate (growing type). Independently of the stage of polymerization, branching due to the direct coupling of filaments with an acute angle to the mother filaments (a coupling type) occurred. Phalloidin suppressed the growing type of branching but not the coupling type, implying that actin monomers are required for the former but not the latter. We found, by single molecule measurements using optical tweezers, that the Arp2/3 complex attaches to the side of actin filaments and the N-WASP appears to detach from the actin-Arp2/3 complex at 6-7 pN.

    Original languageEnglish
    Pages (from-to)1550-1555
    Number of pages6
    JournalBiochemical and Biophysical Research Communications
    Issue number5
    Publication statusPublished - 2002


    • Arp2/3 complex
    • Branching of actin filaments
    • N-WASP
    • Optical tweezers
    • Polymerization of actin
    • Total internal reflection fluorescence microscopy
    • VCA

    ASJC Scopus subject areas

    • Biochemistry
    • Biophysics
    • Molecular Biology


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