Equilibrium and transition between single- and double-headed binding of kinesin as revealed by single-molecule mechanics

Kenji Kawaguchi, Sotaro Uemura, Shin'Ichi Ishiwata*

*この研究の対応する著者

    研究成果: Article査読

    43 被引用数 (Scopus)

    抄録

    Kinesin is a processive motor protein that "walks" on a microtubule toward its plus end. We reported previously that the distribution of unbinding force and elastic modulus for a single kinesin-microtubule complex was either unimodal or bimodal depending on the nucleotide states of the kinesin heads, hence showing that the kinesin may bind the microtubule either with one head or with both heads at once. Here, we found that the shape of the unbinding-force distribution depends both on the loading rate and on the manner of loading not only in the presence of AMP-PNP but also in the absence of nucleotides. Irrespective of the nucleotide state and the loading conditions examined here, the unbinding force obtained by loading directed toward the minus end of microtubule was 45% greater than that for plus end-directed loading. These results could be explained by a model in which equilibrium exists between single- and double-headed binding and the load (F) dependence of lifetime, τ(F), of each binding is expressed by τ(F) = τ(0)exp(-Fd/kBT), where τ(0) is the lifetime without external load and d a characteristic distance, both of which depend on single- or double-headed binding, kB, the Boltzmann constant and T, the absolute temperature. The model analysis showed that the forward and backward rates of transition from single- to doubleheaded binding are 2 and 0.2/s for the AMP-PNP state, and 70 and 7/s for the nucleotide-free state. Moreover, in the presence of AMP-PNP, we detected the moment of transition from single- to double-headed binding through an abrupt increase in the elastic modulus and estimated the transition rate to be ∼1/s, which is consistent with the model analysis.

    本文言語English
    ページ(範囲)1103-1113
    ページ数11
    ジャーナルBiophysical Journal
    84
    2 I
    出版ステータスPublished - 2003 2月 1

    ASJC Scopus subject areas

    • 生物理学

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