Asymmetric Molecular Architecture of the Human γ-Tubulin Ring Complex

Cell. 2020 Jan 9;180(1):165-175.e16. doi: 10.1016/j.cell.2019.12.007. Epub 2019 Dec 17.


The γ-tubulin ring complex (γ-TuRC) is an essential regulator of centrosomal and acentrosomal microtubule formation, yet its structure is not known. Here, we present a cryo-EM reconstruction of the native human γ-TuRC at ∼3.8 Å resolution, revealing an asymmetric, cone-shaped structure. Pseudo-atomic models indicate that GCP4, GCP5, and GCP6 form distinct Y-shaped assemblies that structurally mimic GCP2/GCP3 subcomplexes distal to the γ-TuRC "seam." We also identify an unanticipated structural bridge that includes an actin-like protein and spans the γ-TuRC lumen. Despite its asymmetric architecture, the γ-TuRC arranges γ-tubulins into a helical geometry poised to nucleate microtubules. Diversity in the γ-TuRC subunits introduces large (>100,000 Å2) surfaces in the complex that allow for interactions with different regulatory factors. The observed compositional complexity of the γ-TuRC could self-regulate its assembly into a cone-shaped structure to control microtubule formation across diverse contexts, e.g., within biological condensates or alongside existing filaments.

Keywords: GCP2; GCP3; GCP4; GCP5; GCP6; actin; microtubule nucleation; microtubules; single particle cryo-EM; γ-tubulin ring complex.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Cryoelectron Microscopy / methods
  • HeLa Cells
  • Humans
  • Microtubule-Associated Proteins / metabolism
  • Microtubule-Associated Proteins / ultrastructure
  • Microtubule-Organizing Center / metabolism*
  • Microtubule-Organizing Center / ultrastructure*
  • Microtubules / metabolism
  • Tubulin / metabolism
  • Tubulin / ultrastructure*


  • Actins
  • Microtubule-Associated Proteins
  • TUBGCP4 protein, human
  • TUBGCP5 protein, human
  • TUBGCP6 protein, human
  • Tubulin