5ffi
[2Fe:2S] ferredoxin FeSII from Azotobacter vinelandii[2Fe:2S] ferredoxin FeSII from Azotobacter vinelandii
Structural highlights
FunctionFESII_AZOVI Binds to and protects nitrogenase from irreversible exposure to O(2), in what is known as 'conformational protection' (PubMed:7830548, PubMed:7548055, PubMed:10220344, PubMed:26654855). Shifts nitrogenase into an inactive, O(2)-tolerant state. Exists in 2 states, an open oxidized state that binds and protects nitrogenase, and a closed reduced state that probably does not bind nitrogenase; cooperative oxidation of the 2Fe-2S clusters causes the conformation change (PubMed:26654855). Does not protect nitrogenase with the vanadium-iron subunit, not clear if it protects the iron-only nitrogenase (PubMed:7830548).[1] [2] [3] [4] Publication Abstract from PubMedThe two-component metalloprotein nitrogenase catalyzes the reductive fixation of atmospheric dinitrogen into bioavailable ammonium in diazotrophic prokaryotes. The process requires an efficient energy metabolism, so that although the metal clusters of nitrogenase rapidly decompose in the presence of dioxygen, many free-living diazotrophs are obligate aerobes. In order to retain the functionality of the nitrogen-fixing enzyme, some of these are able to rapidly "switch-off" nitrogenase, by shifting the enzyme into an inactive but oxygen-tolerant state. Under these conditions the two components of nitrogenase form a stable, ternary complex with a small [2Fe:2S] ferredoxin termed FeSII or the "Shethna protein II". Here we have produced and isolated Azotobacter vinelandii FeS II and have determined its three-dimensional structure to 2.1 A resolution by X-ray diffraction. In the crystals, the dimeric protein was present in two distinct states that differ in the conformation of an extended loop in close proximity to the iron-sulfur cluster. We show that this rearrangement is redox-dependent and forms the molecular basis for oxygen-dependent conformational protection of nitrogenase. Protection assays highlight that FeSII binds to a preformed complex of MoFe and Fe protein upon activation, primarily through electrostatic interactions. The surface properties and known complexes of nitrogenase component proteins allow us to propose a model of the conformationally protected ternary complex of nitrogenase. A Conformational Switch Triggers Nitrogenase Protection from Oxygen Damage by Shethna Protein II (FeSII).,Schlesier J, Rohde M, Gerhardt S, Einsle O J Am Chem Soc. 2015 Dec 24. PMID:26654855[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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