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Structure of the γ-tubulin ring complex: a template for microtubule nucleation

Nature Cell Biology volume 2, pages 365–370 (2000)Cite this article

Abstract

The γ-tubulin ring complex (γTuRC) is a protein complex of relative molecular mass ~2.2 × 106 that nucleates microtubules at the centrosome. Here we use electron-microscopic tomography and metal shadowing to examine the structure of isolated Drosophila γTuRCs and the ends of microtubules nucleated by γTuRCs and by centrosomes. We show that the γTuRC is a lockwasher-like structure made up of repeating subunits, topped asymmetrically with a cap. A similar capped ring is also visible at one end of microtubules grown from isolated γTuRCs and from centrosomes. Antibodies against γ-tubulin label microtubule ends, but not walls, in centrosomes. These data are consistent with a template-mediated mechanism for microtubule nucleation by the γTuRC.

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Figure 1: Structure of isolated γ-TuRCs.
Figure 2: Reconstructions of isolated γ-TuRCs in complex with microtubules.
Figure 3: Comparison of ring-wall widths in γ-TuRCs labelled with anti-γ-tubulin antibody and in unlabelled γ-TuRCs.
Figure 4: Reconstructions of microtubule origins in intact centrosomes.
Figure 5: Model for microtubule nucleation by the ‘template’ action of the γ-TuRC.

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Acknowledgements

We thank C. Wiese and Y. Zheng for help with γTuRC preparations, H. Aldaz for suggesting the EZ-link biotin for antibody labelling, T. Keating for sharing data before publication and for advice on the manuscript, B. Keszthelyi for development of improved image reconstruction approaches, R. McQuity for improved software for automated tomography and T. Mitchison for part of M. M.’s salary. This work was supported by the Howard Hughes Medical Institute and NIH grants GM 31627 (to D.A.A.) and GM23928-22 (to T.M.).

Correspondence and requests for materials should be addressed to M.M.

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Authors and Affiliations

  1. Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, 513 Parnassus Avenue, San Francisco, California, 94143, USA

    Michelle Moritz, Michael B. Braunfeld, Vincent Guénebaut & David A. Agard

  2. Department of Cell Biology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, Missouri, 63110, USA

    John Heuser

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Correspondence to Michelle Moritz.

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Moritz, M., Braunfeld, M., Guénebaut, V. et al. Structure of the γ-tubulin ring complex: a template for microtubule nucleation. Nat Cell Biol 2, 365–370 (2000). https://doi.org/10.1038/35014058

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