title: Visualization of ATP synthase dimers in mitochondria by electron cryo-tomography.
abstract: Electron cryo-tomography is a powerful tool in structural biology, capable of visualizing the three-dimensional structure of biological samples, such as cells, organelles, membrane vesicles, or viruses at molecular detail. To achieve this, the aqueous sample is rapidly vitrified in liquid ethane, which preserves it in a close-to-native, frozen-hydrated state. In the electron microscope, tilt series are recorded at liquid nitrogen temperature, from which 3D tomograms are reconstructed. The signal-to-noise ratio of the tomographic volume is inherently low. Recognizable, recurring features are enhanced by subtomogram averaging, by which individual subvolumes are cut out, aligned and averaged to reduce noise. In this way, 3D maps with a resolution of 2 nm or better can be obtained. A fit of available high-resolution structures to the 3D volume then produces atomic models of protein complexes in their native environment. Here we show how we use electron cryo-tomography to study the in situ organization of large membrane protein complexes in mitochondria. We find that ATP synthases are organized in rows of dimers along highly curved apices of the inner membrane cristae, whereas complex I is randomly distributed in the membrane regions on either side of the rows. By subtomogram averaging we obtained a structure of the mitochondrial ATP synthase dimer within the cristae membrane.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Davies
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Bertram
authors.initials: B
authors.lastname: Daum
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Vicki A M
authors.initials: VA
authors.lastname: Gold
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Mühleip
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Tobias
authors.initials: T
authors.lastname: Brandt
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Thorsten B
authors.initials: TB
authors.lastname: Blum
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics.
authors.forename: Deryck J
authors.initials: DJ
authors.lastname: Mills
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics; werner.kuehlbrandt@biophys.mpg.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Kühlbrandt
mesh_terms: D055032:Electron Microscope Tomography / Q000379:methods*; D008928:Mitochondria / Q000201:enzymology*; D025261:Mitochondrial Proton-Translocating ATPases / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D025261:Mitochondrial Proton-Translocating ATPases