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Updated: Sep 28, 2025

High-Resolution Respirometry to Assess Bioenergetics in Cells and Tissues Using Chamber- and Plate-Based Respirometers
Published on: October 26, 2021
Structures of Tetrahymena's respiratory chain reveal the diversity of eukaryotic core metabolism
Long Zhou1, María Maldonado2, Abhilash Padavannil2
1Department of Biophysics and Department of Critical Care Medicine of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.
Abstract:
Respiration is a core biological energy-converting process whose last steps are carried out by a chain of multisubunit complexes in the inner mitochondrial membrane. To probe the functional and structural diversity of eukaryotic respiration, we examined the respiratory chain of the ciliate Tetrahymena thermophila (Tt). Using cryo-electron microscopy on a mixed sample, we solved structures of a supercomplex between Tt complex I (Tt-CI) and Tt-CIII2 (Tt-SC I+III2) and a structure of Tt-CIV2. Tt-SC I+III2 (~2.3 megadaltons) is a curved assembly with structural and functional symmetry breaking. Tt-CIV2 is a ~2.7-megadalton dimer with more than 50 subunits per protomer, including mitochondrial carriers and a TIM83-TIM133-like domain. Our structural and functional study of the T. thermophila respiratory chain reveals divergence in key components of eukaryotic respiration, thereby expanding our understanding of core metabolism.
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