Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, is the first and largest enzyme complex of the respiratory chains of many eukaryotes and most bacteria. It couples the transfer of two electrons from NADH to ubiquinone with the translocation of four protons across the membrane. Dysfunctions of the human complex I are related to the onset of neurodegenerative diseases such as Parkinson’s or Alzheimer’s disease and to ageing. Cryo-electron microscopy and x-ray crystallography revealed the unusual L-shaped structure of the complex consisting of a peripheral and a membrane arm. Both reactions catalyzed by the complex, electron transfer and proton translocation, are beautifully reflected by its architecture: while the peripheral arm catalyzes electron transfer from NADH to (ubi)quinone by means of one non-covalently bound flavin mononucleotide and, depending on the species, eight to ten iron-sulfur (Fe/S) clusters, the membrane arm catalyzes the redox-driven proton translocation through four putative proton-translocation pathways. Both reactions find their putative junction in the (ubi)quinone-binding site, located at the interface between the two arms. It is suggested that the redox reaction in the peripheral arm induces conformational changes that are transmitted to the membrane arm leading to the opening and closing of the channels.
We work with bacterial complex I from Escherichia coli, a structural minimal form of an energy-converting NADH:ubiquinone oxidoreductase. The E. coli complex comprises 13 subunits called NuoA-N that add up to a molecular mass of about 530 kDa. Our group focuses on structure/function relationships of respiratory complex I. We aim at the determination of its 3D structure by x-ray crystallography and cryo-electron microscopy. We determine the influence of mutations on electron transfer and proton translocation. Furthermore, we investigate the assembly of the complex from its individual subunits and seek to identify the chaperones needed for the insertion of the Fe/S clusters. Finally, we characterize the supramolecular organization of the complex in the E. coli cytoplasmic membrane.
References
Schulte, M., Frick, K., Gnandt, E., Jurkovic, S., Burschel, S., Labatzke, R., Aierstock, K., Fiegen, D., Wohlwend, D., Gerhardt, S., Einsle, O. and Friedrich, T. (2019) A mechanism to prevent production of reactive oxygen species by Escherichia coli respiratory complex I. Nat. Commun. 10:2551. DOI: 10.1038/s41467-019-10429
Sonn-Segev, A., Belacic, K., Bodrug, T., Young, G., VanderLinden, R.T., Schulman, B.A., Schimpf, J., Friedrich, T., Dip, P.V., Schwartz, T.U., Bauer, B., Peters, J.-M., Struwe, W.B., Benesch, J.L.P., Brown, N.G., Haselbach, D. and Kukura, P. (2020) Quantifying the heterogeneity of macromolecular machines by mass photometry. Nat. Commun. 11:1772. DOI: 10.1038/s41467-020-15642-w
Nuber, F., Merono, L., Oppermann, S., Schimpf, J., Wohlwend, D. and Friedrich, T. (2021) A quinol anion as catalytic intermediate coupling proton translocation with electron transfer in E. coli respiratory complex I. Front. Chem., 9, 672969. DOI: 10.3389/fchem.2021.672969
Schimpf, J., Oppermann, S., Gerasimova, T., Santos Seica, A.F., Hellwig, P., Grishkovskaya, I., Wohlwend, D., Haselbach, D. and Friedrich, T. (2021) Structure of the peripheral arm of a minimalistic respiratory complex I. Structure 30, 80-94.e4. DOI: 10.1016/j.str.2021.09.005
Hoeser, F., Tausend, H., Götz, S., Wohlwend, D., Einsle, O., Günther, S. and Friedrich, T. (2022) Respiratory complex I with charge symmetry in the membrane arm pumps protons. Proc. Natl. Acad. Sci., 119, e2123090119. DOI: 10.1073/pnas.2123090119
