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    Loop L5 assumes three distinct orientations during the ATpase cycle of the mitotic kinesin eg5: a transient and time-resolved flourescence study

    Muretta, J.M. and Behnke-Parks, W.M. and Major, J. and Petersen, K.J. and Goulet, A. and Moores, Carolyn A. and Thomas, D.D. and Rosenfeld, S.S. (2013) Loop L5 assumes three distinct orientations during the ATpase cycle of the mitotic kinesin eg5: a transient and time-resolved flourescence study. Journal of Biological Chemistry 288 (48), pp. 34839-34849. ISSN 0021-9258.

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    Members of the kinesin superfamily of molecular motors differ in several key structural domains, which probably allows these molecular motors to serve the different physiologies required of them. One of the most variable of these is a stem-loop motif referred to as L5. This loop is longest in the mitotic kinesin Eg5, and previous structural studies have shown that it can assume different conformations in different nucleotide states. However, enzymatic domains often consist of a mixture of conformations whose distribution shifts in response to substrate binding or product release, and this information is not available from the "static" images that structural studies provide. We have addressed this issue in the case of Eg5 by attaching a fluorescent probe to L5 and examining its fluorescence, using both steady state and time-resolved methods. This reveals that L5 assumes an equilibrium mixture of three orientations that differ in their local environment and segmental mobility. Combining these studies with transient state kinetics demonstrates that there is a major shift in this distribution during transitions that interconvert weak and strong microtubule binding states. Finally, in conjunction with previous cryo-EM reconstructions of Eg5·microtubule complexes, these fluorescence studies suggest a model in which L5 regulates both nucleotide and microtubule binding through a set of reversible interactions with helix α3. We propose that these features facilitate the production of sustained opposing force by Eg5, which underlies its role in supporting formation of a bipolar spindle in mitosis.


    Item Type: Article
    Keyword(s) / Subject(s): anisotropy decay, cryo-EM, Eg5, electron microscopy (EM), fluorescence, kinesin, kinetics, microtubules, stopped flow, time-resolved fluorescence
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
    Research Centres and Institutes: Structural Molecular Biology, Institute of (ISMB)
    Depositing User: Sarah Hall
    Date Deposited: 29 Jan 2014 14:57
    Last Modified: 02 Aug 2023 17:09


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