Structures of Tetrahymena thermophila respiratory megacomplexes on the tubular mitochondrial cristae

Nat Commun. 2023 May 29;14(1):2542. doi: 10.1038/s41467-023-38158-5.


Tetrahymena thermophila, a classic ciliate model organism, has been shown to possess tubular mitochondrial cristae and highly divergent electron transport chain involving four transmembrane protein complexes (I-IV). Here we report cryo-EM structures of its ~8 MDa megacomplex IV2 + (I + III2 + II)2, as well as a ~ 10.6 MDa megacomplex (IV2 + I + III2 + II)2 at lower resolution. In megacomplex IV2 + (I + III2 + II)2, each CIV2 protomer associates one copy of supercomplex I + III2 and one copy of CII, forming a half ring-shaped architecture that adapts to the membrane curvature of mitochondrial cristae. Megacomplex (IV2 + I + III2 + II)2 defines the relative position between neighbouring half rings and maintains the proximity between CIV2 and CIII2 cytochrome c binding sites. Our findings expand the current understanding of divergence in eukaryotic electron transport chain organization and how it is related to mitochondrial morphology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Mitochondria / metabolism
  • Mitochondrial Membranes / metabolism
  • Tetrahymena thermophila* / genetics