The structure of the γ-tubulin small complex: Implications of its architecture and flexibility for microtubule nucleation

Justin M. Kollman, Alex Zelter, Eric G D Muller, Bethany Fox, Luke M. Rice, Trisha N. Davis, David A. Agard

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

The γ-tubulin small complex (γ-TuSC) is an evolutionarily conserved heterotetramer essential for microtubule nucleation. We have determined the structure of the Saccharomyces cerevisiae γ-TuSC at 25-Å resolution by electron microscopy. γ-TuSC is Y-shaped, with an elongated body connected to two arms. Gold labeling showed that the two γ-tubulins are located in lobes at the ends of the arms, and the relative orientations of the other γ-TuSC components were determined by in vivo FRET. The structures of different subpopulations of γ-TuSC indicate flexibility in the connection between a mobile arm and the rest of the complex, resulting in variation of the relative positions and orientations of the γ-tubulins. In all of the structures, the γ-tubulins are distinctly separated, a configuration incompatible with the microtubule lattice. The separation of the γ-tubulins in isolated γ-TuSC likely plays a role in suppressing its intrinsic microtubule-nucleating activity, which is relatively weak until the γ-TuSC is incorporated into higher order complexes or localized to microtubule-organizing centers. We propose that further movement of the mobile arm is required to bring the γ-tubulins together in microtubule-like interactions, and provide a template for microtubule growth.

Original languageEnglish (US)
Pages (from-to)207-215
Number of pages9
JournalMolecular biology of the cell
Volume19
Issue number1
DOIs
StatePublished - Jan 1 2008

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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