Mycothiazole enables structural characterization of entire ubiquinone-accessing tunnel in mitochondrial respiratory complex I
- 1Kyoto University
Abstract
Mitochondrial NADH-ubiquinone (UQ) oxidoreductase (respiratory complex I) reduces UQ within its long tunnel-like cavity, which is coupled to triggering proton translocation at the membrane domain. Although mammalian complex I adopts distinct "open" and "closed" conformations, the architecture of the UQ-accessing tunnel in the open conformation remains poorly defined owing to partial disorder of the UQ catalytic region near Fe-S cluster N2 in the tunnel. Here, we applied cryo-electron microscopy (EM) single particle analysis to determine the structures of complex I in bovine heart submitochondrial particles in the presence or absence of a mycothiazole-type inhibitor. Preceding photoaffinity labeling experiments using a synthetic photoreactive derivative ([125I]pMT) revealed that mycothiazole specifically labels the 49-kDa and ND1 subunits, both of which form a part of the UQ-accessing tunnel. Cryo-EM analysis demonstrated that bound mycothiazole reorganizes and stabilizes the UQ catalytic region in both open and closed conformations, enabling the first complete structural modeling of the entire UQ-accessing tunnel in the open conformation. Unexpectedly, in the presence of bound mycothiazole, loops of the PSST subunit forming the catalytic region in the tunnel adopted closed conformation-like features, whereas open conformation-like features were determined for the transmembrane helices of ND1 and ND6 subunits. The present study revealed that bound mycothiazole can reorganize the UQ catalytic region in the UQ-accessing tunnel and lead to a hybrid conformational state beyond the canonical open-versus-closed conformational model.
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BibTeX
@misc{akisada2026mycothiazole,
title = {{Mycothiazole enables structural characterization of entire ubiquinone-accessing tunnel in mitochondrial respiratory complex I}},
author = {S. Akisada and R. Otani and T. Masuya and S. Miyako and H. Saito and K. Mitsuoka and H. Miyoshi and K. Yokoyama and M. Murai},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.01.756109},
url = {https://www.biorxiv.org/content/10.64898/2026.10.01.756109v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Mycothiazole enables structural characterization of entire ubiquinone-accessing tunnel in mitochondrial respiratory complex I
AU - S. Akisada
AU - R. Otani
AU - T. Masuya
AU - S. Miyako
AU - H. Saito
AU - K. Mitsuoka
AU - H. Miyoshi
AU - K. Yokoyama
AU - M. Murai
PY - 2026
DA - 2026/10/01
PB - bioRxiv
DO - 10.64898/2026.10.01.756109
UR - https://www.biorxiv.org/content/10.64898/2026.10.01.756109v1
AB - Mitochondrial NADH-ubiquinone (UQ) oxidoreductase (respiratory complex I) reduces UQ within its long tunnel-like cavity, which is coupled to triggering proton translocation at the membrane domain. Although mammalian complex I adopts distinct "open" and "closed" conformations, the architecture of the UQ-accessing tunnel in the open conformation remains poorly defined owing to partial disorder of the UQ catalytic region near Fe-S cluster N2 in the tunnel. Here, we applied cryo-electron microscopy (EM) single particle analysis to determine the structures of complex I in bovine heart submitochondrial particles in the presence or absence of a mycothiazole-type inhibitor. Preceding photoaffinity labeling experiments using a synthetic photoreactive derivative ([125I]pMT) revealed that mycothiazole specifically labels the 49-kDa and ND1 subunits, both of which form a part of the UQ-accessing tunnel. Cryo-EM analysis demonstrated that bound mycothiazole reorganizes and stabilizes the UQ catalytic region in both open and closed conformations, enabling the first complete structural modeling of the entire UQ-accessing tunnel in the open conformation. Unexpectedly, in the presence of bound mycothiazole, loops of the PSST subunit forming the catalytic region in the tunnel adopted closed conformation-like features, whereas open conformation-like features were determined for the transmembrane helices of ND1 and ND6 subunits. The present study revealed that bound mycothiazole can reorganize the UQ catalytic region in the UQ-accessing tunnel and lead to a hybrid conformational state beyond the canonical open-versus-closed conformational model.
ER -