PT  - JOURNAL ARTICLE
AU  - Ahmed-Noor A. Agip
AU  - Injae Chung
AU  - Alvaro Sanchez-Martinez
AU  - Alexander J. Whitworth
AU  - Judy Hirst
TI  - Cryo-EM structures of mitochondrial respiratory complex I from <em>Drosophila melanogaster</em>
AID  - 10.1101/2022.11.01.514700
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.11.01.514700
4099  - http://biorxiv.org/content/early/2022/11/01/2022.11.01.514700.short
4100  - http://biorxiv.org/content/early/2022/11/01/2022.11.01.514700.full
AB  - Respiratory complex I powers ATP synthesis by oxidative phosphorylation, exploiting the energy from NADH oxidation by ubiquinone to drive protons across an energy-transducing membrane. Drosophila melanogaster is a candidate model organism for complex I due to its high evolutionary conservation with the mammalian enzyme, well-developed genetic toolkit, and complex physiology for studies in specific cell types and tissues. Here, we isolate complex I from Drosophila and determine its structure, revealing a 43-subunit assembly with high structural homology to its 45-subunit mammalian counterpart, including a hitherto unknown homologue to subunit NDUFA3. The major conformational state of the Drosophila enzyme is the mammalian-type ‘ready-to-go’ active resting state, with a fully ordered and enclosed ubiquinone-binding site, but a subtly altered global conformation related to changes in subunit ND6. The mammalian-type ‘deactive’ pronounced resting state is not observed: in two minor states the ubiquinone-binding site is unchanged, but a deactive-type π-bulge is present in ND6-TMH3. Our detailed structural knowledge of Drosophila complex I provides a foundation for new approaches to disentangle mechanisms of complex I catalysis and regulation in bioenergetics and physiology.Competing Interest StatementThe authors have declared no competing interest.