The cryo-EM structure of a γ-TuSC elucidates architecture and regulation of minimal microtubule nucleation systems

Nat Commun. 2020 Nov 11;11(1):5705. doi: 10.1038/s41467-020-19456-8.

Abstract

The nucleation of microtubules from αβ-tubulin subunits is mediated by γ-tubulin complexes, which vary in composition across organisms. Aiming to understand how de novo microtubule formation is achieved and regulated by a minimal microtubule nucleation system, we here determined the cryo-electron microscopy structure of the heterotetrameric γ-tubulin small complex (γ-TuSC) from C. albicans at near-atomic resolution. Compared to the vertebrate γ-tubulin ring complex (γ-TuRC), we observed a vastly remodeled interface between the SPC/GCP-γ-tubulin spokes, which stabilizes the complex and defines the γ-tubulin arrangement. The relative positioning of γ-tubulin subunits indicates that a conformational rearrangement of the complex is required for microtubule nucleation activity, which follows opposing directionality as predicted for the vertebrate γ-TuRC. Collectively, our data suggest that the assembly and regulation mechanisms of γ-tubulin complexes fundamentally differ between the microtubule nucleation systems in lower and higher eukaryotes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Candida albicans / chemistry
  • Candida albicans / metabolism*
  • Cryoelectron Microscopy
  • Evolution, Molecular
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Guanosine Diphosphate / metabolism
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism
  • Microtubules / metabolism*
  • Models, Molecular
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Mutation
  • Protein Conformation
  • Tubulin / chemistry*

Substances

  • Fungal Proteins
  • Microtubule-Associated Proteins
  • Multiprotein Complexes
  • Tubulin
  • Guanosine Diphosphate