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Exploration of Arsenite Oxidase: An Ancient Bioenergetic Enzyme in Archaeal Electron Transfer

This study examines the structure and function of arsenite oxidase, an ancient bioenergetic enzyme found in *Alcaligenes faecalis*. Utilizing electron transfer chains and transmembrane helices, this enzyme plays a crucial role in the oxidation of arsenite (AsIII) to arsenate (AsV) while contributing to ATP synthesis. Initial results indicate that the Rieske protein associated with the arsenite oxidase operon is membrane-associated and participates in light-oxidation processes within the photosynthetic electron transfer chains of *Chloroflexus aurantiacus*, a thermophilic photosynthetic bacterium.

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Exploration of Arsenite Oxidase: An Ancient Bioenergetic Enzyme in Archaeal Electron Transfer

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  1. Arsenite oxidase, an ancient bioenergetic enzyme?

  2. ATPase Electron transfer chain H+

  3. Hélice transmembranaire Cluster [2Fe-2S] Domaine soluble

  4. arsenite oxidase from Alcaligenes faecalis Ellis et al. 2001 Structure 9, 125-132

  5. Distribution of arsenite oxidases on the phylo tree of species

  6. ssu-rRNA:

  7. Chloroflexusaurantiacus - thermophilic photosynthetic bacterium (affiliated to Thermus-group) - isolated from a Yellowstone Park hot spring - earliest branching phototroph in standard ssu rRNA-trees - genome sequenced no bc-complex in Chloroflexus (genome), sole Rieske protein in the arsenite oxidase operon Inital results: - Rieske protein is membrane-associated (no RPE signal in supernatant) - Rieske protein can be light-oxidised, i.e. electrons from AsIII oxidation enter the photosynthetic electron transfer chain

  8. ATPase Electron transfer chain H+

  9. - hn + AsIII ? AsV Chloroflexus in the presence of arsenite ATPase mena- quinone photo- system arsox AuCy H+

  10. Rieske [3Fe4S] Mo cyt c Alcaligenes faecalis oxidase AsIII/ AsV Em (mV) Chloroflexus aurantiacus 0 Mo ? [3Fe4S] ? Rieske 100 AuCy ? 200 P/P+ (photosystem) 300

  11. BIP 09/CNRS Marseile Frauke Baymann (CR1) Anne-Lise Ducluzeau (Mastère) Simon Duval (Mastère) Evelyne Lebrun (CR1) Wolfgang Nitschke (DR2) Barbara Schoepp (CR1)

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