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Nat Struct Mol Biol. 2015 Feb;22(2):132-7. doi: 10.1038/nsmb.2953. Epub 2015 Jan 19.

Ring closure activates yeast γTuRC for species-specific microtubule nucleation.

Author information

1
Department of Biochemistry, University of Washington, Seattle, Washington, USA.
2
1] Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, California, USA. [2] Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California, USA. [3] California Institute for Quantitative Biosciences (QB3), University of California at San Francisco, San Francisco, California, USA.
3
Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California, USA.
4
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
5
Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
6
1] Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California, USA. [2] Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California, USA.

Abstract

The γ-tubulin ring complex (γTuRC) is the primary microtubule nucleator in cells. γTuRC is assembled from repeating γ-tubulin small complex (γTuSC) subunits and is thought to function as a template by presenting a γ-tubulin ring that mimics microtubule geometry. However, a previous yeast γTuRC structure showed γTuSC in an open conformation that prevents matching to microtubule symmetry. By contrast, we show here that γ-tubulin complexes are in a closed conformation when attached to microtubules. To confirm the functional importance of the closed γTuSC ring, we trapped the closed state and determined its structure, showing that the γ-tubulin ring precisely matches microtubule symmetry and providing detailed insight into γTuRC architecture. Importantly, the closed state is a stronger nucleator, thus suggesting that this conformational switch may allosterically control γTuRC activity. Finally, we demonstrate that γTuRCs have a strong preference for tubulin from the same species.

PMID:
25599398
PMCID:
PMC4318760
DOI:
10.1038/nsmb.2953
[Indexed for MEDLINE]
Free PMC Article

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