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Spectroscopic Evidence for Site Specific Chemistry at a Unique Iron Site of the [4Fe−4S] Cluster in Ferredoxin:Thioredoxin Reductase
Auteur(s)
Jameson, Guy N. L.
Editeur(s)
Walters, Elizabeth M.
Manieri, Wanda
Schürmann, Peter
Johnson, Michael K.
Hanh Huynh, Boi
Date de parution
2003
In
Journal of the American Chemical Society (JACS), American Chemical Society (ACS), 2003/125/5/1146–1147
Résumé
Ferredoxin:thioredoxin reductase (FTR) catalyzes the reduction of the disulfide in thioredoxin in two one-electron steps using an active site comprising a [4Fe−4S] in close proximity to a redox active disulfide. Mössbauer spectroscopy has been used to investigate the ligation and electronic properties of the [4Fe−4S] cluster in as-prepared FTR which has the active-site disulfide intact and in the <i>N</i>-ethylmaleimide (NEM)-modified form which provides a stable analogue of the one-electron-reduced heterodisulfide intermediate and has one of the cysteines of the active-site disulfide alkylated with NEM. The results reveal novel site-specific cluster chemistry involving weak interaction of the active-site disulfide with a unique Fe site of the [4Fe−4S]<sup>2+</sup> cluster in the resting enzyme and cleavage of the active-site disulfide with concomitant coordination of one of the cysteines to yield a [4Fe−4S]<sup>3+</sup> cluster with a five-coordinate Fe site ligated by two cysteine residues in the NEM-modified enzyme. The results provide molecular-level insight into the catalytic mechanism of FTR and other Fe−S-cluster-containing disulfide reductases, and suggest a possible mechanism for the reductive cleavage of S-adenosylmethionine by the radical SAM family of Fe−S enzymes.
Autre version
http://dx.doi.org/10.1021/ja029338e
Type de publication
Resource Types::text::journal::journal article
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