9CU0

Azotobacter vinelandii 1:1:1 MoFeP:FeP:FeSII-Complex (C1 symmetry)

Summary for 9CU0

• Entry DOI: 10.2210/pdb9cu0/pdb
• EMDB information: 45924
• Descriptor: Nitrogenase molybdenum-iron protein alpha chain, MAGNESIUM ION, IRON/SULFUR CLUSTER, ... (13 entities in total)
• Functional Keywords: nitrogenase, femoco, nitrogen, p-cluster, metal binding protein
• Biological source: Azotobacter vinelandii; More
• Total number of polymer chains: 7
• Total formula weight: 311055.45

Authors

Narehood, S.M.,Cook, B.D.,Srisantitham, S.,Eng, V.H.,Shiau, A.,Britt, R.D.,Herzik, M.A.,Tezcan, F.A. (deposition date: 2024-07-25, release date: 2025-01-15, Last modification date: 2025-02-05)

Primary citation

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.
Structural basis for the conformational protection of nitrogenase from O 2 .
Nature, 637:991-997, 2025

PubMed Abstract: The low reduction potentials required for the reduction of dinitrogen (N) render metal-based nitrogen-fixation catalysts vulnerable to irreversible damage by dioxygen (O). Such O 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-respiring organisms to support the high energy demand of catalytic N reduction. To counter O damage to nitrogenase, diazotrophs use O scavengers, exploit compartmentalization or maintain high respiration rates to minimize intracellular O concentrations. A last line of damage control is provided by the 'conformational protection' mechanism, in which a [2Fe:2S] ferredoxin-family protein termed FeSII (ref. ) is activated under O stress to form an O-resistant complex with the nitrogenase component proteins. Despite previous insights, the molecular basis for the conformational O 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-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.

PubMed: 39779844
DOI: 10.1038/s41586-024-08311-1

Experimental method

ELECTRON MICROSCOPY (3.94 Å)