Journal: Nature / Year: 2025 Title: Electron flow in hydrogenotrophic methanogens under nickel limitation. Authors: Shunsuke Nomura / Pablo San Segundo-Acosta / Evgenii Protasov / Masanori Kaneko / Jörg Kahnt / Bonnie J Murphy / Seigo Shima / Abstract: Methanogenic archaea are the main producers of the potent greenhouse gas methane. In the methanogenic pathway from CO and H studied under laboratory conditions, low-potential electrons for CO ...Methanogenic archaea are the main producers of the potent greenhouse gas methane. In the methanogenic pathway from CO and H studied under laboratory conditions, low-potential electrons for CO reduction are generated by a flavin-based electron-bifurcation reaction catalysed by heterodisulfide reductase (Hdr) complexed with the associated [NiFe]-hydrogenase (Mvh). F-reducing [NiFe]-hydrogenase (Frh) provides electrons to the methanogenic pathway through the electron carrier F (ref. ). Here we report that under strictly nickel-limited conditions, in which the nickel concentration is similar to those often observed in natural habitats, the production of both [NiFe]-hydrogenases in Methanothermobacter marburgensis is strongly downregulated. The Frh reaction is substituted by a coupled reaction with [Fe]-hydrogenase (Hmd), and the role of Mvh is taken over by F-dependent electron-donating proteins (Elp). Thus, Hmd provides all electrons for the reducing metabolism under these nickel-limited conditions. Biochemical and structural characterization of Elp-Hdr complexes confirms the electronic interaction between Elp and Hdr. The conservation of the genes encoding Elp and Hmd in CO-reducing hydrogenotrophic methanogens suggests that the Hmd system is an alternative pathway for electron flow in CO-reducing hydrogenotrophic methanogens under nickel-limited conditions.
Applied symmetry - Point group: C1 (asymmetric) / Algorithm: FOURIER SPACE / Resolution.type: BY AUTHOR / Resolution: 2.3 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 4) Details: Particles are C2-symmetry expanded Final refinement made in CryoSparc using Local refinement Number images used: 234858
Initial angle assignment
Type: MAXIMUM LIKELIHOOD
Final angle assignment
Type: MAXIMUM LIKELIHOOD
Final 3D classification
Number classes: 3 / Software - Name: RELION
FSC plot (resolution estimation)
-
Atomic model buiding 1
Initial model
Chain - Source name: Other / Chain - Initial model type: other / Details: Automated-based model building using Model Angelo
Refinement
Space: REAL / Protocol: RIGID BODY FIT
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