Molecular architecture of the augmin complex

Nat Commun. 2022 Sep 16;13(1):5449. doi: 10.1038/s41467-022-33227-7.

Abstract

Accurate segregation of chromosomes during mitosis depends on the correct assembly of the mitotic spindle, a bipolar structure composed mainly of microtubules. The augmin complex, or homologous to augmin subunits (HAUS) complex, is an eight-subunit protein complex required for building robust mitotic spindles in metazoa. Augmin increases microtubule density within the spindle by recruiting the γ-tubulin ring complex (γ-TuRC) to pre-existing microtubules and nucleating branching microtubules. Here, we elucidate the molecular architecture of augmin by single particle cryo-electron microscopy (cryo-EM), computational methods, and crosslinking mass spectrometry (CLMS). Augmin's highly flexible structure contains a V-shaped head and a filamentous tail, with the head existing in either extended or contracted conformational states. Our work highlights how cryo-EM, complemented by computational advances and CLMS, can elucidate the structure of a challenging protein complex and provides insights into the function of augmin in mediating microtubule branching nucleation.

MeSH terms

  • Cryoelectron Microscopy
  • Microtubule-Associated Proteins* / metabolism
  • Microtubules / metabolism
  • Spindle Apparatus / metabolism
  • Tubulin* / metabolism

Substances

  • Microtubule-Associated Proteins
  • Tubulin