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  4. Role of Histidine-86 in the Catalytic Mechanism of Ferredoxin: Thioredoxin Reductase
 
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Role of Histidine-86 in the Catalytic Mechanism of Ferredoxin: Thioredoxin Reductase

Auteur(s)
Walters, Elizabeth M.
Garcia-Serres, Ricardo
Naik, Sunil G.
Bourquin, Florence
Glauser, Dominique A.
Schürmann, Peter 
Institut de biologie 
Huynh, Boi Hanh
Johnson, Michael K.
Date de parution
2009
In
Biochemistry, American Chemical Society (ACS), 2009/48/5/1016-1024
Résumé
Ferredoxin:thioredoxin reductase catalyzes the reduction of thioredoxins in plant chloroplasts using the [Fe<sub>2</sub>S<sub>2</sub>] ferredoxin as a one-electron donor and as such plays a central role in light regulation of oxygenic photosynthesis. The active-site comprises a [Fe<sub>4</sub>S<sub>4</sub>] cluster next to a redox-active disulfide that is cleaved in sequential one-electron steps and the combination of spectroscopic and crystallographic studies have revealed a catalytic mechanism involving novel site specific cluster chemistry in the oxidized, one-electron- and two-electron-reduced redox states. Histidine-86 has emerged as a potential proton donor/acceptor in the catalytic mechanism based on redox-related changes in the positioning of the imidazole ring during redox cycling and greatly decreased activity for the H86Y variant. Here we report on spectroscopic and redox characterization of the [Fe<sub>4</sub>S<sub>4</sub>] center in <i>Synechocystis</i> sp. PCC 6803 H86Y ferredoxin:thoredoxin reductase in the accessible redox states of both the as purified and N-ethylmaleimide-modified forms, using the combination of UV−visible absorption and variable-temperature magnetic circular dichroism, EPR, resonance Raman and Mössbauer spectroscopies. The results demonstrate that His86 is required for formation of the partially valence-localized [Fe<sub>4</sub>S</sub>4</sub>]<sup>2+</sup> cluster that is the hallmark of two-electron-reduced intermediate. Taken together with the available structural data, the spectroscopic results indicate a functional role for His86 in protonation/deprotonation of the cluster-interacting thiol and anchoring the cluster interacting thiol in close proximity to the cluster in the two-electron-reduced intermediate.
Identifiants
https://libra.unine.ch/handle/123456789/4441
_
10.1021/bi802074p
Type de publication
journal article
Dossier(s) à télécharger
 main article: Walters_Elizabeth_M._-_Role_of_Histidine-86_in_the_Catalytic_20170630.pdf (2.08 MB)
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