Profiles

Christoph von Ballmoos

Christoph von Ballmoos

Forskare

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Arbetar vid Institutionen för biokemi och biofysik
Telefon 08-16 37 29
E-post christoph.von.ballmoos@dbb.su.se
Besöksadress Svante Arrhenius väg 16
Rum A 467
Postadress Institutionen för biokemi och biofysik 106 91 Stockholm

Om mig

Understanding cellular respiration at a molecular level

ATP is required for many energy consuming processes in cellular life. Most of it is produced by the ATP synthase, a rotary engine that recycles ATP from ADP and phosphate. The energy for the rotary mechanism is stored as a transmembrane electrochemical proton gradient, maintained by respiratory chain enzymes. This general principle of respiration and ATP synthesis is universally conserved, but special adaptations are found in diverse species.

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Figure 1. Ion cycling across biological membranes leading to ATP synthesis. In different species, specialized proteins create a transmembrane electrochemical proton/sodium gradient. These gradients serve as energy sources for ATP synthesis from ADP and inorganic phosphate by an F1F0 ATP synthase.

 

Ongoing and planned projects in the lab

  • We incorporate ATP synthase and cytochrome c oxidase in a lipid vesicle called liposome, mimicking their function in a living cell. Using different lipid compositions, engineered variants of the two enzymes, we try to unravel the mechanism of the proton transfer in and between the two enzymes.
  • Many small organisms live under extreme conditions, facing an alkaline environment or very high temperatures. Lipid bilayers become more permeable to protons facing these conditions, and efficiency in energy coupling is reduced. An additional complication is found in alkaliphilic bacteria where the environmental pH is much higher than the cytoplasmic pH that is kept constant around neutral. As a consequence, the electrochemical proton gradient in these organisms is inversed and disadvantageous for ATP synthesis. Using purified enzymes (ATP synthase, cytochrome c oxidase) and lipid extracts from alkaliphilic/ thermophilic bacteria, we aim to understand their strategies to circumvent these energetic difficulties.

 

 

It has been proposed that proton transfer between the lipid head groups of a membrane surface is significantly faster than that between the lipid head groups and the surrounding water phase. Consequently, a proton pumped by a respiratory oxidase would be conducted in two dimensions along the surface over long distances before being released to the bulk solution. In a densely packed cellular membrane, the proton is thus more likely to be picked up by another cellular pump (e.g. ATP synthase) that pumps the proton back to the other side of the membrane. If such a scenario were true, local acidification of the membrane surface would greatly increase the driving force for ATP synthesis, absorbing at least part of the energetic penalties in alkaliphilic bacteria. We aim to experimentally investigate this hypothesis with different experimental approaches.

 

Selected publications

  • Näsvik Öjemyr, L., von Ballmoos, C., Gennis, R. B., Sligar, S. G., & Brzezinski, P. (2012). Reconstitution of respiratory oxidases in membrane nanodiscs for investigation of proton-coupled electron transfer. FEBS letters, 586(5), 640-5
  • von Ballmoos, C., Gennis, R. B., Ädelroth, P., & Brzezinski, P. (2011). Kinetic design of the respiratory oxidases. Proceedings of the National Academy of Sciences of the United States of America, 108(27), 11057-11062.
  • von Ballmoos, C., Wiedenmann, A., & Dimroth, P. (2009). Essentials for ATP synthesis by F1F0 ATP synthases. Annual Review of Biochemistry, 78(1), 649-672.
  • von Ballmoos, C., Cook, G. M., & Dimroth, P. (2008). Unique rotary ATP synthase and its biological diversity. Annual Review of Biophysics, 37, 43-64.
  • Wiedenmann, A., Dimroth, P., & Von Ballmoos, C. (2009). Functional asymmetry of the F0 motor in bacterial ATP synthases. Molecular Microbiology, 72(2), 479-490.
 

Senast uppdaterad: 25 maj 2018

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