MZT Proteins Form Multi-Faceted Structural Modules in the γ-Tubulin Ring Complex

Cell Rep. 2020 Jun 30;31(13):107791. doi: 10.1016/j.celrep.2020.107791.

Abstract

Microtubule organization depends on the γ-tubulin ring complex (γ-TuRC), a ∼2.3-MDa nucleation factor comprising an asymmetric assembly of γ-tubulin and GCP2-GCP6. However, it is currently unclear how the γ-TuRC-associated microproteins MZT1 and MZT2 contribute to the structure and regulation of the holocomplex. Here, we report cryo-EM structures of MZT1 and MZT2 in the context of the native human γ-TuRC. MZT1 forms two subcomplexes with the N-terminal α-helical domains of GCP3 or GCP6 (GCP-NHDs) within the γ-TuRC "lumenal bridge." We determine the X-ray structure of recombinant MZT1/GCP6-NHD and find it is similar to that within the native γ-TuRC. We identify two additional MZT/GCP-NHD-like subcomplexes, one of which is located on the outer face of the γ-TuRC and comprises MZT2 and GCP2-NHD in complex with a centrosomin motif 1 (CM1)-containing peptide. Our data reveal how MZT1 and MZT2 establish multi-faceted, structurally mimetic "modules" that can expand structural and regulatory interfaces in the γ-TuRC.

Keywords: CDK5Rap2; GCP2; GCP3; GCP6; MZT1; MZT2; actin; cryo-EM; microtubule nucleation; γ-tubulin ring complex.

Publication types

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

MeSH terms

  • HeLa Cells
  • Humans
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism*
  • Models, Molecular
  • Multiprotein Complexes / metabolism*
  • Multiprotein Complexes / ultrastructure
  • Peptides / metabolism
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Secondary
  • Tubulin / chemistry
  • Tubulin / metabolism*
  • Tubulin / ultrastructure

Substances

  • MZT1 protein, human
  • Microtubule-Associated Proteins
  • Multiprotein Complexes
  • Peptides
  • TUBGCP3 protein, human
  • TUBGCP6 protein, human
  • Tubulin