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The structure of the gamma-tubulin small complex: implications of its architecture and flexibility for microtubule nucleation.

The gamma-tubulin small complex (gamma-TuSC) is an evolutionarily conserved heterotetramer essential for microtubule nucleation. We have determined the structure of the Saccharomyces cerevisiae gamma-TuSC at 25-A resolution by electron microscopy. gamma-TuSC is Y-shaped, with an elongated body connected to two arms. Gold labeling showed that the two gamma-tubulins are located in lobes at the ends of the arms, and the relative orientations of the other gamma-TuSC components were determined by in vivo FRET. The structures of different subpopulations of gamma-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 gamma-tubulins. In all of the structures, the gamma-tubulins are distinctly separated, a configuration incompatible with the microtubule lattice. The separation of the gamma-tubulins in isolated gamma-TuSC likely plays a role in suppressing its intrinsic microtubule-nucleating activity, which is relatively weak until the gamma-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 gamma-tubulins together in microtubule-like interactions, and provide a template for microtubule growth.

Pubmed ID: 17978090

Authors

  • Kollman JM
  • Zelter A
  • Muller EG
  • Fox B
  • Rice LM
  • Davis TN
  • Agard DA

Journal

Molecular biology of the cell

Publication Data

January 3, 2008

Associated Grants

  • Agency: NIGMS NIH HHS, Id: F32 GM-078790
  • Agency: NCRR NIH HHS, Id: P41 RR-011823
  • Agency: NCRR NIH HHS, Id: P41 RR011823
  • Agency: NIGMS NIH HHS, Id: R01 GM-040506
  • Agency: NIGMS NIH HHS, Id: R01 GM-31627
  • Agency: NIGMS NIH HHS, Id: R01 GM040506
  • Agency: Howard Hughes Medical Institute, Id:

Mesh Terms

  • Fluorescence Resonance Energy Transfer
  • Microscopy, Electron
  • Microtubules
  • Models, Molecular
  • Nucleotides
  • Pliability
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Tubulin