Biology subjects

von Ballmoos, C.

Publications and source records attributed to von Ballmoos, C..

5 recordsLinked to original sources

bioRxiv2026

Compartmentalized oxygen generation from hydrogen peroxide enables anaerobic oxidative phosphorylation and confers a fitness advantage

Hydrogen peroxide is a host-derived reactive oxygen species that invading bacteria must detoxify to overcome the host defence. It was previously proposed that cytoplasmic catalase converts this peroxide into molecular oxygen, allowing facultative anaerobes such as Escherichia coli and Salmonella to respire in oxygen-limited niches. Here, we experimentally test this mechanism by reconstituting a minimal system comprising bovine catalase and purified E. coli quinol oxidases in liposomes. We find that catalase-generated oxygen sustains quinol oxidation under anaerobic conditions, and the rapid consumption keeps the environment effectively oxygen-free. When F1FO ATP synthase is included into the proteoliposomes, the system generates a protonmotive force that drives ATP synthesis, with activity scaling with hydrogen peroxide concentration. Competition experiments at low peroxide concentrations demonstrate that compartmentalized oxygen production provides a decisive advantage, as liposomes lacking catalase are strongly outcompeted. All three terminal quinol oxidases of E. coli were tested and shown to support ATP synthesis in vitro, suggesting that bd-II involvement in vivo is likely due to regulation of gene expression rather than catalytic constraints. Together, our data show that intracellular oxygen generation from host-derived peroxide enables oxidative phosphorylation in globally anaerobic, electron-acceptor-limited environments such as the gut, thereby providing a mechanistic explanation for the observed fitness advantage.

biochemistry↗

bioRxiv2026

Rescue of pATOM36-depleted T. brucei by human MTCH1/2 reveals common features of protein insertases

Alpha-helically anchored proteins of the mitochondrial outer membrane depend on dedicated insertases, including the MIM complex in yeast, pATOM36 in trypanosomes, and MTCH1/MTCH2 in humans. These insertases lack sequence homology and arose by convergent evolution. Here we show that MTCH1 and an N-terminally modified MTCH2 can replace the OMM biogenesis function of trypanosomal pATOM36, demonstrating functional compatibility across a large phylogenetic distance. Moreover, like other insertases, pATOM36 has lipid scramblase activity and likely induces local membrane thinning. Structural modeling reveals that even though they have inverted membrane topologies, pATOM36 and MTCH1/MTCH2 adopt a similar architecture. They form a hydrophilic cavity comprising five transmembrane helices that is open to both the cytosol and laterally to the membrane core. The same features also extend to the large phylogenetically unrelated YidC-like insertase family of bacterial origin. Together, these findings suggest that membrane protein insertion is constrained to a small number of viable mechanistic solutions, providing evidence for "deterministic" evolution acting at the molecular level.

biochemistry↗

bioRxiv2025

Hydrogenase-driven ATP synthesis from air

All cells require a continuous supply of the universal energy currency, adenosine triphosphate (ATP), to drive countless cellular reactions. The universally conserved F1Fo-ATP synthase regenerates ATP from ADP and Pi by harnessing a transmembrane electrochemical proton gradient (pmf). Bacteria have evolved a wide diversity of pmf-forming proteins to make ATP using light, organic, and inorganic energy sources. Recently, we proposed that many bacteria survive using atmospheric trace gases to produce ATP when limited for other energy sources. However, there is no direct proof that atmospheric energy sources are sufficient to generate pmf or drive ATP synthesis. Here, we show that the membrane-associated hydrogen:quinone oxidoreductase Huc from Mycobacterium smegmatis enables ATP synthesis from air. Purified Huc couples H2 oxidation to the reduction of various ubiquinone and menaquinone analogues. We designed and optimised a minimal respiratory chain in which Huc is reconstituted into liposomes with a pmf-generating terminal oxidase and the ATP-generating F1Fo-ATP synthase. Our experiments show that passive hydrogen exchange from air to solution is sufficient for the electron transfer and pmf generation required to accumulate ATP. Finally, by combining continuous culture bioenergetics measurements with theoretical calculations, we show this process is sufficient for mycobacteria to sustain pmf and ATP synthesis (two ATP molecules per H2 oxidised) for maintenance energy requirements during nutrient starvation. These findings prove that atmospheric energy sources are dependable lifeline substrates that enable continuous energy conservation during nutrient starvation. In addition, this work provides a new tool for ATP production in synthetic applications, which unlike other approaches is traceless without by-product accumulation.

microbiology↗

bioRxiv2021

Experimental platform for the functional investigation of membrane proteins in giant unilamellar vesicles

Giant unilamellar vesicles (GUVs) are micrometer-sized model membrane systems that can be viewed directly under the microscope. They serve as scaffolds for the bottom-up creation of synthetic cells, targeted drug delivery and have been used in many in vitro studies of membrane related phenomena. GUVs are also of interest for the functional investigation of membrane proteins that carry out many key cellular functions. A major hurdle to a wider application of GUVs in this field is the diversity of existing protocols that are optimized for individual proteins. Here, we compare PVA assisted and electroformation techniques for GUV formation under physiologically relevant conditions, and analyze the effect of immobilization on vesicle structure and membrane tightness towards small substrates and protons. There, differences in terms of yield, size, and leakage of GUVs produced by PVA assisted swelling and electroformation were found, dependent on salt and buffer composition. Using fusion of oppositely charged membranes to reconstitute a model membrane protein, we find that empty vesicles and proteoliposomes show similar fusion behavior, which allows for a rapid estimation of protein incorporation using fluorescent lipids.

synthetic biology↗

bioRxiv2021

Functional design of bacterial superoxide:quinone oxidoreductase

The superoxide anion - molecular oxygen reduced by a single electron - is produced in large amounts by enzymatic and adventitious reactions and can perform a range of cellular functions, including bacterial warfare and iron uptake, signalling and host immune response in eukaryotes. However, it also serves as precursor for more deleterious species such as the hydroxyl anion or peroxynitrite and therefore, cellular defense mechanisms for superoxide neutralization have evolved. In addition to the soluble proteins superoxide dismutase and superoxide reductase, recently the membrane embedded diheme cytochrome b561(CybB) from E. coli has been proposed to act as a superoxide:quinone oxidoreductase. Here, we confirm superoxide and cellular ubiquinones or menaquinones as natural substrates and show that quinone binding to the enzyme accelerates the reaction with superoxide. The reactivity of the substrates is in accordance with the here determined midpoint potential of the two b hemes (+48 and -23 mV / NHE). Our data suggest that the enzyme can work near the diffusion limit in the forward direction and can also catalyse the reverse reaction efficiently under physiological conditions. The data is discussed in context of described cytochrome b561 proteins and potential physiological roles of CybB.

biochemistry↗