Journal Article

PUBDB-2026-01327

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Hydroxo-bridged active site of flavodiiron NO reductase revealed by NRVS and DFT

Folgosa, F. ; Pelmenschikov, V. (Corresponding author) ; Caserta, G.Extern* ; Keck, M. ; Lorent, C.Extern* ; Laun, K.Extern* ; Yoda, Y. ; Gee, L.Extern* ; Kaupp, M. ; Tamasaku, K.Extern*XFEL.EU* ; Birrell, J.Extern* ; Sergeev, I.XFEL.EU*DESY* ; Limberg, C. ; Teixeira, M. ; Lauterbach, L. (Corresponding author)Extern*

2026
National Acad. of Sciences Washington, DC

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Please use a persistent id in citations: doi:10.1073/pnas.2512429123  doi:10.3204/PUBDB-2026-01327

Abstract: The use of oxygen and nitrate as terminal electron acceptors provides organisms with a huge amount of available energy but necessitates methods to detoxify reactive intermediates. The mechanisms of NO and O$_2$ detoxification in many organisms involve flavodiiron proteins (FDPs). Although the proteinaceous ligands that coordinate the diiron active site of these enzymes are well established, its exact coordination environment remains under debate due to conflicting interpretations of crystallographic and spectroscopic/theoretical studies. Using $^{57}$Fe nuclear resonance vibrational spectroscopy (NRVS), complemented by Mössbauer spectroscopy and density functional theory, we elucidated the redox-linked structural changes in the FDP from Escherichia coli. The as-isolated diferric state is best described as a dihydroxo-bridged Fe(III)–(μOH−)$_2$–Fe(III) core, which upon reduction converts to a monohydroxo Fe(II)–(μOH−)–Fe(II) center through the loss of one bridging ligand. This ligand rearrangement defines the structural basis for redox-linked reactivity in FDPs. The study further demonstrates that photoreduction of a stable metalloprotein species can occur under NRVS conditions, indicating that synchrotron-based vibrational measurements may induce subtle redox changes even under low photon flux. These find-ings provide a mechanistic framework for interpreting redox-linked ligand dynamics in diiron enzymes and highlight the need to collect damage-free X-ray crystal structures avoiding potential beam-induced reduction. Furthermore, diiron active sites are found in numerous other enzyme classes (e.g., methane monooxygenase), and therefore, our findings have implications way beyond the FDPs.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. PETRA-S (FS-PETRA-S)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
3. DFG project G:(GEPRIS)273919336 - SPP 1927: Iron-Sulfur for Life (273919336) (273919336)
4. DFG project G:(GEPRIS)390540038 - EXC 2008: Unifying Systems in Catalysis "UniSysCat" (390540038) (390540038)
5. DFG project G:(GEPRIS)390919832 - EXC 2186: Das Fuel Science Center – Adaptive Umwandlungssysteme für erneuerbare Energie- und Kohlenstoffquellen (390919832) (390919832)
6. TIMB3 - Twin to Illuminate Metals in Biology and Biocatalysis through Biospectroscopy (810856) (810856)
7. FS-Proposal: I-20210059 (I-20210059) (I-20210059)

Experiment(s):

1. PETRA Beamline P01 (PETRA III)

Appears in the scientific report 2026

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Database coverage:
; ; ; BIOSIS Previews ; Biological Abstracts ; Clarivate Analytics Master Journal List ; Current Contents - Agriculture, Biology and Environmental Sciences ; Current Contents - Life Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 10 ; JCR ; National-Konsortium ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection ; Zoological Record

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