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  • 1.
    Lundgren, Camilla A. K
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjöstrand, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Biner, Olivier
    Bennett, Matthew
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Rudling, Axel
    Johansson, Ann-Louise
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Brzezinsk, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Carlsson, Jens
    von Ballmoos, Christoph
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Scavenging of superoxide by a membrane-bound superoxide oxidase2018In: Nature Chemical Biology, ISSN 1552-4450, E-ISSN 1552-4469, Vol. 14, p. 788-793Article in journal (Refereed)
    Abstract [en]

    Superoxide is a reactive oxygen species produced during aerobic metabolism in mitochondria and prokaryotes. It causes damage to lipids, proteins and DNA and is implicated in cancer, cardiovascular disease, neurodegenerative disorders and aging. As protection, cells express soluble superoxide dismutases, disproportionating superoxide to oxygen and hydrogen peroxide. Here, we describe a membrane-bound enzyme that directly oxidizes superoxide and funnels the sequestered electrons to ubiquinone in a diffusion-limited reaction. Experiments in proteoliposomes and inverted membranes show that the protein is capable of efficiently quenching superoxide generated at the membrane in vitro. The 2.0 Å crystal structure shows an integral membrane di-heme cytochrome b poised for electron transfer from the P-side and proton uptake from the N-side. This suggests that the reaction is electrogenic and contributes to the membrane potential while also conserving energy by reducing the quinone pool. Based on this enzymatic activity, we propose that the enzyme family be denoted superoxide oxidase (SOO).

  • 2.
    Nitharwal, Ram Gopal
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schäfer, Jacob
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wiseman, Benjamin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjöstrand, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Kuang, Qie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ädelroth, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Brzezinski, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Biochemical and structural characterization of a superoxide dismutase-containing respiratory supercomplex from Mycobacterium smegmatisManuscript (preprint) (Other academic)
  • 3.
    Sjöstrand, Dan
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Diamanti, Riccardo
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lundgren, Camilla A. K.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wiseman, Benjamin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A rapid expression and purification condition screening protocol for membrane protein structural biology2017In: Protein Science, ISSN 0961-8368, E-ISSN 1469-896X, Vol. 26, no 8, p. 1653-1666Article in journal (Refereed)
    Abstract [en]

    Membrane proteins control a large number of vital biological processes and are often medically important-not least as drug targets. However, membrane proteins are generally more difficult to work with than their globular counterparts, and as a consequence comparatively few high-resolution structures are available. In any membrane protein structure project, a lot of effort is usually spent on obtaining a pure and stable protein preparation. The process commonly involves the expression of several constructs and homologs, followed by extraction in various detergents. This is normally a time-consuming and highly iterative process since only one or a few conditions can be tested at a time. In this article, we describe a rapid screening protocol in a 96-well format that largely mimics standard membrane protein purification procedures, but eliminates the ultracentrifugation and membrane preparation steps. Moreover, we show that the results are robustly translatable to large-scale production of detergent-solubilized protein for structural studies. We have applied this protocol to 60 proteins from an E. coli membrane protein library, in order to find the optimal expression, solubilization and purification conditions for each protein. With guidance from the obtained screening data, we have also performed successful large-scale purifications of several of the proteins. The protocol provides a rapid, low cost solution to one of the major bottlenecks in structural biology, making membrane protein structures attainable even for the small laboratory.

  • 4.
    Smirnova, Irina A.
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Moscow State University, Russian Federation.
    Sjöstrand, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Li, Fei
    Björck, Markus
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schäfer, Jacob
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Östbye, Henrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stanford University, United States.
    von Ballmoos, Christoph
    Lander, Gabriel C.
    Ädelroth, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Brzezinski, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Isolation of yeast complex IV in native lipid nanodiscs2016In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1858, no 12, p. 2984-2992Article in journal (Refereed)
    Abstract [en]

    We used the amphipathic styrene maleic acid (SMA) co-polymer to extract cytochrome c oxidase (CytcO) in its native lipid environment from S. cerevisiae mitochondria. Native nanodiscs containing one CytcO per disc were purified using affinity chromatography. The longest cross-sections of the native nanodiscs were 11 nm x 14 nm. Based on this size we estimated that each CytcO was surrounded by similar to 100 phospholipids. The native nanodiscs contained the same major phospholipids as those found in the mitochondrial inner membrane. Even though CytcO forms a supercomplex with cytochrome bc(1) in the mitochondria! membrane, cyt.bc(1) was not found in the native nanodiscs. Yet, the loosely-bound Respiratory SuperComplex factors were found to associate with the isolated CytcO. The native nanodiscs displayed an O-2-reduction activity of similar to 130 electrons CytcO(-1) s(-1) and the kinetics of the reaction of the fully reduced CytcO with 02 was essentially the same as that observed with CytcO in mitochondrial membranes. The kinetics of CO-ligand binding to the CytcO catalytic site was similar in the native nanodiscs and the mitochondrial membranes. We also found that excess SMA reversibly inhibited the catalytic activity of the mitochondrial CytcO, presumably by interfering with cyt. c binding. These data point to the importance of removing excess SMA after extraction of the membrane protein. Taken together, our data shows the high potential of using SMA-extracted CytcO for functional and structural studies.

  • 5.
    Wiseman, Benjamin
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nitharwal, Ram Gopal
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Fedotovskaya, Olga
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schäfer, Jacob
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Guo, Hui
    Kuang, Qie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Benlekbir, Samir
    Sjöstrand, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ädelroth, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Rubinstein, John L.
    Brzezinski, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Structure of a functional obligate complex III2IV2 respiratory supercomplex from Mycobacterium smegmatis2018In: Nature Structural & Molecular Biology, ISSN 1545-9993, E-ISSN 1545-9985, Vol. 25, no 12, p. 1128-1136Article in journal (Refereed)
    Abstract [en]

    In the mycobacterial electron-transport chain, respiratory complex III passes electrons from menaquinol to complex IV, which in turn reduces oxygen, the terminal acceptor. Electron transfer is coupled to transmembrane proton translocation, thus establishing the electrochemical proton gradient that drives ATP synthesis. We isolated, biochemically characterized, and determined the structure of the obligate III2IV2 supercomplex from Mycobacterium smegmatis, a model for Mycobacterium tuberculosis. The supercomplex has quinol:O-2 oxidoreductase activity without exogenous cytochrome c and includes a superoxide dismutase subunit that may detoxify reactive oxygen species produced during respiration. We found menaquinone bound in both the Q(o) and Q(i) sites of complex III. The complex III-intrinsic diheme cytochrome cc subunit, which functionally replaces both cytochrome c(1) and soluble cytochrome c in canonical electron-transport chains, displays two conformations: one in which it provides a direct electronic link to complex IV and another in which it serves as an electrical switch interrupting the connection.

  • 6.
    Zhou, Shu
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pettersson, Pontus
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Huang, Jingjing
    Sjöholm, Johannes
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjöstrand, Dan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pomes, Regis
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Brzezinski, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Mäler, Lena
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ädelroth, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Solution NMR structure of yeast Rcf1, a protein involved in respiratory supercomplex formation2018In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 115, no 12, p. 3048-3053Article in journal (Refereed)
    Abstract [en]

    The Saccharomyces cerevisiae respiratory supercomplex factor 1 (Rcf1) protein is located in the mitochondrial inner membrane where it is involved in formation of supercomplexes composed of respiratory complexes III and IV. We report the solution structure of Rcf1, which forms a dimer in dodecylphosphocholine (DPC) micelles, where each monomer consists of a bundle of five transmembrane (TM) helices and a short flexible soluble helix (SH). Three TM helices are unusually charged and provide the dimerization interface consisting of 10 putative salt bridges, defining a charge zipper motif. The dimer structure is supported by molecular dynamics (MD) simulations in DPC, although the simulations show a more dynamic dimer interface than the NMR data. Furthermore, CD and NMR data indicate that Rcf1 undergoes a structural change when reconstituted in liposomes, which is supported by MD data, suggesting that the dimer structure is unstable in a planar membrane environment. Collectively, these data indicate a dynamic monomer-dimer equilibrium. Furthermore, the Rcf1 dimer interacts with cytochrome c, suggesting a role as an electron-transfer bridge between complexes III and IV. The Rcf1 structure will help in understanding its functional roles at a molecular level.

1 - 6 of 6
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