Download MendeleyStructural basis for the conformational protection of nitrogenase from O 2 .
Narehood, S.M., Cook, B.D., Srisantitham, S., Eng, V.H., Shiau, A.A., McGuire, K.L., Britt, R.D., Herzik Jr., M.A., Tezcan, F.A.(2025) Nature 637: 991-997
- PubMed: 39779844 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1038/s41586-024-08311-1
- Primary Citation Related Structures:
9CTZ, 9CU0, 9CU1, 9CU2 - PubMed Abstract:
The low reduction potentials required for the reduction of dinitrogen (N 2 ) render metal-based nitrogen-fixation catalysts vulnerable to irreversible damage by dioxygen (O 2 ) 1-3 . Such O 2 sensitivity represents a major conundrum for the enzyme nitrogenase, as a large fraction of nitrogen-fixing organisms are either obligate aerobes or closely associated with O 2 -respiring organisms to support the high energy demand of catalytic N 2 reduction 4 . To counter O 2 damage to nitrogenase, diazotrophs use O 2 scavengers, exploit compartmentalization or maintain high respiration rates to minimize intracellular O 2 concentrations 4-8 . A last line of damage control is provided by the 'conformational protection' mechanism 9 , in which a [2Fe:2S] ferredoxin-family protein termed FeSII (ref. 10 ) is activated under O 2 stress to form an O 2 -resistant complex with the nitrogenase component proteins 11,12 . Despite previous insights, the molecular basis for the conformational O 2 protection of nitrogenase and the mechanism of FeSII activation are not understood. Here we report the structural characterization of the Azotobacter vinelandii FeSII-nitrogenase complex by cryo-electron microscopy. Our studies reveal a core complex consisting of two molybdenum-iron proteins (MoFePs), two iron proteins (FePs) and one FeSII homodimer, which polymerize into extended filaments. In this three-protein complex, FeSII mediates an extensive network of interactions with MoFeP and FeP to position their iron-sulphur clusters in catalytically inactive but O 2 -protected states. The architecture of the FeSII-nitrogenase complex is confirmed by solution studies, which further indicate that the activation of FeSII involves an oxidation-induced conformational change.
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
Organizational Affiliation:
