Publications

Benedens M, Rosales-Hernandez C, Straathof SAP, Loschwitz J, Berninghausen O, Maglia G, Beckmann R, Kedrov A
Assembly and the gating mechanism of the Pel exopolysaccharide export complex PelBC of Pseudomonas aeruginosa.
Nat Commun (2025), 16(1):5249; doi.org/10.1038/s41467-025-60605-8

Abstract: The pathogen Pseudomonas aeruginosa enhances its virulence and antibiotic resistance upon formation of durable biofilms. The exopolysaccharides Pel, Psl and alginate essentially contribute to the biofilm matrix, but their secretion mechanisms are barely understood. Here, we reveal the architecture of the outer membrane complex PelBC for Pel export, where the essential periplasmic ring of twelve lipoproteins PelC is mounted on top of the nanodisc-embedded β-barrel PelB. The PelC assembly is stabilized by electrostatic contacts with the periplasmic rim of PelB and via the membrane-anchored acyl chains. The negatively charged interior of the PelB β-barrel forms a route for the cationic Pel exopolysaccharide. The β-barrel is sealed at the extracellular side, but molecular dynamic simulations suggest that the short loop Plug-S is sufficiently flexible to open a tunnel for the exopolysaccharide transport. This gating model is corroborated by single-channel conductivity measurements, where a deletion of Plug-S renders a constitutively open β-barrel. Our structural and functional analysis offers a comprehensive view on this pathogenicity-relevant complex and suggests the route taken by the exopolysaccharide at the final secretion step.

Groh M, Lettau E, Schoknecht J, Liedtke J, Lauterbach L, Leimkühler S
Biocatalytic cofactor regeneration for CO₂ reduction: Integration of a hydrogenase and a formate dehydrogenase in H₂-driven systems.
Journal of CO2 Utilization (2024) Vol. 83, 102828; doi.org/10.1016/j.jcou.2024.102828

Abstract: Formate dehydrogenases catalyze the reversible oxidation of formate to carbon dioxide. These enzymes play an important role in CO₂ reduction and serve as nicotinamide cofactor recycling enzymes. More recently, the CO₂-reducing activity of formate dehydrogenases, especially metal-containing formate dehydrogenases, has been further explored for efficient atmospheric CO₂ capture. In this sense, molecular hydrogen (H₂) as the fuel of the future represents an efficient, cheap and environmentally friendly reducing agent when produced from renewable sources. Hydrogenases are enzymes that catalyze the reversible oxidation of H₂. Herein, the functional interplay between the soluble [NiFe] hydrogenase from Cupriavidus necator and the molybdenum-dependent formate dehydrogenase from Rhodobacter capsulatus was investigated in a coupled biocatalytic system. H₂-driven CO₂ reduction (H₂CO₂R) using methyl viologen as an artificial electron mediator gave a higher product yield of formate than using NAD⁺ as the physiological electron mediator. The enzymes were stable under anaerobic conditions for 18 h, making the coupled reaction suitable for biotechnological purposes.