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Structural Basis for Microtubule Binding and Release by Dynein

Science  21 Sep 2012:
Vol. 337, Issue 6101, pp. 1532-1536
DOI: 10.1126/science.1224151

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Motoring Along

Dyneins are large and complex molecular motors that transport cargo along cellular microtubules and power the movement of cilia. An enigma is how microtubule binding and nucleotide hydrolysis are coordinated between sites separated by 25 nm. Redwine et al. (p. 1532) report an electron microscopy structure of the dynein microtubule-binding domain bound to microtubules in a high-affinity state and combined this with molecular dynamics and existing x-ray structures to provide a model for how dynein couples its affinity for microtubules with the nucleotide-bound state of the motor domain.

Abstract

Cytoplasmic dynein is a microtubule-based motor required for intracellular transport and cell division. Its movement involves coupling cycles of track binding and release with cycles of force-generating nucleotide hydrolysis. How this is accomplished given the ~25 nanometers separating dynein’s track- and nucleotide-binding sites is not understood. Here, we present a subnanometer-resolution structure of dynein’s microtubule-binding domain bound to microtubules by cryo–electron microscopy that was used to generate a pseudo-atomic model of the complex with molecular dynamics. We identified large rearrangements triggered by track binding and specific interactions, confirmed by mutagenesis and single-molecule motility assays, which tune dynein’s affinity for microtubules. Our results provide a molecular model for how dynein’s binding to microtubules is communicated to the rest of the motor.

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