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Electron Cryomicroscopy Investigation of the Proton CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector e4 Abstracts opening a large membrane pore, potentiated by inducers such as the P3 & P4.3 phosphate, the depletion of adenine nucleotides and the presence of thiol oxidants. It leads to the swelling of the mitochondria, loss of Electron cryomicroscopy investigation of the proton-conducting proton motive force, disruption of ion homeostasis and hydrolysis of pore of ATP synthase ATP by the ATP synthase. These events have been linked to pathways John Rubinstein leading to cell death, and to human diseases including cardiac The Hospital for Sick Children Research Institute, 686 Bay Street, ischemia and muscle dystrophy. We have examined this proposal, Rm. 20-9705, Toronto, ON, Canada fi and a summary of our ndings will be presented. E-mail: [email protected] Adenosine triphosphate (ATP) synthases use the energy stored in doi:10.1016/j.bbabio.2014.05.120 a transmembrane proton-motive force to synthesize ATP from aden- osine diphosphate (ADP) and inorganic phosphate. The transloca- tion of protons across the membrane region of the complex leads to P3 & P4.2 rotation of a rotor subcomplex that drives conformational changes in the enzyme's membrane-extrinsic catalytic region. The mechanism by Structural basis for the coupling mechanism of respiratory which proton translocation induces rotation is not known. Here, we complex I, a giant molecular proton pump present structural data from single particle electron cryomicroscopy Leonid Sazanov (cryo-EM) that gives insight into the architecture of the membrane- Mitochondrial Biology Unit, Medical Research Council, Cambridge, UK bound motors of ATP synthases and related enzymes. This evidence E-mail: [email protected] supports a two-half channel model for proton translocation. NADH-ubiquinone oxidoreductase (complex I) is the first and doi:10.1016/j.bbabio.2014.05.122 largest enzyme in the respiratory chain of mitochondria and many bacteria. It couples electron transfer between NADH and ubiquinone to the translocation of four protons across the membrane. It is a major contributor to the proton flux used for ATP generation in mito- P3 & P4.4 chondria, being one of the key enzymes essential for life as we know it. Mutations in complex I lead to the most common human genetic Mechanistic and structural studies of heme–copper containing disorders. It is an L-shaped assembly formed by membrane and hy- terminal oxidases of the A- and C-families drophilic arms. Mitochondrial complex I consists of 44 subunits of Hartmut Michela, Martin Kohlstaedta, Florian Hilbersa,1, Hao Xiea, about 1 MDa in total, while the prokaryotic enzyme is simpler and Sabine Buschmanna, Florian Langera, Jessica H. van Wonderena, generally consists of 14 conserved “core” subunits. We use the bac- Fraser MacMillanb terial enzyme as a “minimal” model to understand the mechanism of aMax Planck Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt complex I. We have determined all currently known atomic structures am Main, Germany of complex I, starting with the hydrophilic domain [1,2], followed by bHenry Wellcome Unit for Biological EPR, School of Chemistry, University of the membrane domain [3,4] and, finally, the recent structure of the East Anglia, Norwich NR4 7TJ, UK entire Thermus thermophilus complex (536 kDa, 16 subunits, 9 Fe–S 1Present address: Department of Molecular Biology and Genetics, Aarhus clusters, 64 TM helices) [5], the largest asymmetric membrane protein University, Gustav Wieds Vej 10c, 8000 Aarhus C, Denmark. structure solved so far. Structures suggest a unique mechanism of E-mail: [email protected] coupling between electron transfer in the hydrophilic domain and proton translocation in the membrane domain, via long-range (up to We have recently determined the structure of a cbb3 cytochrome Å ~200 ) conformational changes. In order to elucidate the details of c oxidase (C-family), isoform 1, from Pseudomonas stutzericiq [3]. The the coupling mechanism, we are determining crystal structures of the P. stutzeri genome possesses two operons for cbb3 cytochrome c entire complex in different redox states with various substrates/ oxidases, but only isoform 2 has a gene coding for a Q-subunit. We inhibitors bound. Comparison of the structures sheds light on the have recently identified a 34 amino acid peptide which replaces the putative conformational changes during the catalytic cycle, which will Q-subunit in isoform 2. The results of our comparison of isoforms 1 be discussed on the basis of the latest data. and 2 will be presented. References References [1] P. Hinchliffe, L.A. Sazanov, Organization of iron–sulfur clusters [1] J. Kocuck, I. von der Hocht, F. Hilbers, H. Michel, I. Weidinger, in respiratory complex I, Science 309 (2005) 771. Resonance Raman characterization of the ammonia-generated [2] L.A. Sazanov, P. Hinchliffe, Structure of the hydrophilic domain oxo intermediate of cytochrome c oxidase from Paracoccus of respiratory complex I from Thermus thermophilus, Science 311 denitrificans, Biochemistry 52 (2013) 6197–6202. (2006) 1430. [2] I. von der Hocht, J.H. van Wonderen, F. Hilbers, H. Angerer, F. [3] R.G. Efremov, R. Baradaran, L.A. Sazanov, The architecture of Macmillan, H. Michel, Interconversions of P and F intermediates respiratory complex I, Nature 465 (2010) 441. of cytochrome c oxidase from Paracoccus denitrificans, Proc. Natl. [4] R.G. Efremov, L.A. Sazanov, Structure of the membrane domain Acad. Sci. U. S. A. 108 (2011) 3964–3969. of respiratory complex I, Nature 476 (2011) 414. [3] S. Buschmann, E. Warkentin, H. Xie, J.D. Langer, U. Ermler, H. [5] R. Baradaran, J.M. Berrisford, G.S. Minhas, L.A. Sazanov, Crystal Michel, The structure of cbb3 cytochrome oxidase provides insights structure of the entire respiratory complex I, Nature 494 (2013) 443 into proton pumping, Science 329 (2010) 327–330 doi:10.1016/j.bbabio.2014.05.121 doi:10.1016/j.bbabio.2014.05.123.
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