Monomeric γ-Tubulin Nucleates Microtubules*
- From the Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, 91198 Gif-sur-Yvette, France
Abstract
γ-Tubulin is required for nucleation and polarized organization of microtubules in vivo. The mechanism of microtubule nucleation by γ-tubulin and the role of associated proteins is not understood. Here we show that in vitro translated monomeric γ-tubulin nucleates microtubules by lowering the size of the nucleus from seven to three tubulin subunits. In capping the minus end with high affinity (1010 m −1) and a binding stoichiometry of one molecule of γ-tubulin/microtubule, γ-tubulin establishes the critical concentration of the plus end in the medium and prevents minus end growth. γ-Tubulin interacts strongly with β-tubulin. A structural model accounts for these results.
Footnotes
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↵* This work was supported by the Association pour la Recherche contre le Cancer.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Supported by Association pour la Recherche contre le Cancer and the Ligue Nationale contre le Cancer.
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↵§ To whom correspondence should be addressed. Tel.: (33) 01 69 82 34 65; Fax: (33) 01 69 82 31 29; E-mail: carlier@lebs.cnrs-gif.fr.
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Published, JBC Papers in Press, April 7, 2000, DOI 10.1074/jbc.M000688200
- Abbreviations:
- γ-TuRC
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γ-tubulin-ring complex
- MES
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4-morpholineethanesulfonic acid
- GCP
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γ-tubulin complex protein
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- Received January 24, 2000.
- Revision received March 20, 2000.
- The American Society for Biochemistry and Molecular Biology, Inc.
