BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:From Nitrogen Fixation to Carbon Valorization: Engineering Nitroge nases for New Chemistry - CH-636 DTSTART:20261208T161500 DTEND:20261208T171500 DTSTAMP:20261109T180215Z UID:9d191fca8fc3355e5744cd66ee6e27e0d95b59aa277ff58872684b63 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Johannes Rebelein (University Düsseldorf & Forschungsze ntrum Jülich)\nSpeaker: Prof. Dr. Johannes Rebelein (University Düsseld orf & Forschungszentrum Jülich)\n\nAbstract: Nitrogenases are the only k nown enzymes that catalyze the reduction of molecular nitrogen (N2) to amm onia (NH3)\, and with this driving the global nitrogen cycle. Besides the conversion of N2\, we showed that nitrogenases convert carbon dioxide (CO2 ) to carbon monoxide\, formate and hydrocarbons (1-3)\, suggesting new pat hways for CO2 activation and the formation of value-added products.\nThe m echanistic basis and structural determinants for these activities\, substr ate specificity and product profiles remain poorly understood. We demonstr ated that the iron (Fe)-nitrogenase reduces CO₂ nearly threefold more ef ficiently than the canonical molybdenum (Mo) nitrogenase (2). This catalyt ic preference is conserved in vivo\, where Rhodobacter capsulatus strains expressing the Fe-nitrogenase physiologically convert CO₂ to formate and methane. Leveraging high-resolution cryo-EM (3-5)\, we map structural fea tures governing substrate channeling and catalysis of nitrogenase(-like) e nzymes\, to obtain a better understanding of the structure-function relati onship (Figure 1\, 3-6). Why do the different nitrogenase isoforms\, the m olybdenum (Mo)\, the vanadium (V) and the iron (Fe) nitrogenase have diffe rent activities and specificities for the reduction of N2\, CO and CO2? Ev en more surprising is that the nitrogenase-like methylthio-alkane reductas e cleaves carbon-sulfur bonds in vivo and is unable to activate N2 althoug h it harbors a nitrogenase P- and L-cluster (5). \nGuided by these insigh ts\, we engineered nitrogenase variants that shift the product profile tow ard hydrocarbons and significantly enhance CO₂ reduction selectivity in the presence of N₂ (3). These findings redefine nitrogenase substrate pr omiscuity\, provide a mechanistic blueprint for engineering CO₂-reducing biocatalysts\, and establish Fe-nitrogenase as a promising platform for s ustainable carbon valorization.\n \n\n© 2026 EPFL\n\n\nFigure 1. A schem atic overview of FeMoco maturase\, Mo-nitrogenase and methylthio-alkane re ductase with their contained metalloclusters responsible for electron tran sfer and catalysis. The catalyzed main reactions are shown below.\n\nRefer ences :\n\n\n N. N. Oehlmann\, J. G. Rebelein\, ChemBioChem 23\, e20210045 3 (2022).\n N. N. Oehlmann et al.\, Sci. Adv. 10\, eado7729 (2024).\n N. N . Oehlmann et al.\, bioRxiv. doi:10.64898/2026.07.08.737278 (2026).\n F. V . Schmidt et al.\, Nat. Struct. Mol. Biol. 31\, 150-158 (2024).\n Lago-Mac iel et al.\, Nat. Catal. 8\, 1086-1099 (2025).\n Lago-Maciel et al.\, Tren ds Biochem. Sci. 51\, 187-202 (2026).\n\n\nBiography: Prof. Dr. Johannes Rebelein is Professor of Sustainable Biotechnology at Heinrich Heine Unive rsity Düsseldorf and Director of the Institute for Molecular Enzyme Techn ology (IMET) at Forschungszentrum Jülich. His research focuses on metallo enzyme biochemistry and catalysis\, particularly nitrogenase and nitrogena se-like enzymes. Combining biochemical\, structural\, synthetic microbiolo gy and enzyme-engineering approaches\, his group investigates how complex metallocofactors convert small molecules\, including nitrogen and carbon d ioxide\, and how these principles can be harnessed to develop sustainable biotechnological solutions for greenhouse-gas valorization and artificial metalloenzyme design.\nBefore his appointment in Düsseldorf/Jülich\, Reb elein led an Emmy Noether Research Group at the Max Planck Institute for T errestrial Microbiology in Marburg and was a Junior Group Leader at the LO EWE Center for Synthetic Microbiology at Philipps-University Marburg. He c ompleted postdoctoral training with Prof. Thomas Ward at the University of Basel and earned his Ph.D. in Biological Sciences at the University of Ca lifornia\, Irvine\, under Prof. Markus W. Ribbe. He holds B.Sc. and M.Sc. degrees in Biotechnology\, with honors\, from TU Braunschweig. Prof. Rebel ein’s contributions to the field have been recognized with several prest igious honors\, including the European Molecular Biology Organization (EMB O) Young Investigator Award and the VAAM (Association for General and Appl ied Microbiology) Research Award.\n  LOCATION:CE 1 105 https://plan.epfl.ch/?room==CE%201%20105 STATUS:CONFIRMED END:VEVENT END:VCALENDAR