title: Characterisation of the components of the thioredoxin system in the archaeon Sulfolobus solfataricus.
abstract: The thioredoxin system is a redox machinery widely distributed in nature and involved in several cellular functions. It is constituted of thioredoxin reductase (Trx-B), its protein substrate thioredoxin (Trx-A) and NADPH. We have previously characterised a Trx-B from the hyperthermophile Sulfolobus solfataricus (SsTrx-B3) (Ruocco et al. in Biochimie 86:883-892, 2004). As in the genome of this archaeon, the gene coding for another Trx-B (SsTrx-B2) and for two Trx-A (SsTrx-A1, SsTrx-A2) have been putatively identified, these proteins were obtained as recombinant forms and characterised. SsTrx-B2, different from SsTrx-B3, did not elicit a thioredoxin reductase activity. S. solfataricus possessed only one Trx-B (SsTrx-B3), which had two thioredoxins (SsTrx-A1 and SsTrx-A2) as substrates. These latter showed a homodimeric structure and catalysed insulin reduction using either DTT or NADPH/SsTrx-B3 as electron donors. In addition, the electron transfer between SsTrx-B3 and either SsTrx-A1 or SsTrx-A2 was fully reversible, thus allowing the determination of the redox potential of the thioredoxin system in S. solfataricus. Among the two thioredoxins, SsTrx-A2 appeared slightly more active and stable than SsTrx-A1. These data, besides shedding light on thioredoxin system in S. solfataricus, will contribute to add further information on this key enzyme system in Archaea.
authors.affiliation: Dipartimento di Scienze Farmacobiologiche, Università di Catanzaro Magna Graecia, Complesso Ninì Barbieri, 88021, Roccelletta di Borgia, Catanzaro, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Grimaldi
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Ruocco
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: Lanzotti
authors.forename: Alessia
authors.initials: A
authors.lastname: Ruggiero
authors.forename: Immacolata
authors.initials: I
authors.lastname: Ruggiero
authors.forename: Paolo
authors.initials: P
authors.lastname: Arcari
authors.forename: Luigi
authors.initials: L
authors.lastname: Vitagliano
authors.forename: Mariorosario
authors.initials: M
authors.lastname: Masullo
mesh_terms: D001665:Binding Sites; D001671:Biochemistry / Q000379:methods; D002384:Catalysis; D004220:Disulfides; D004591:Electrophoresis, Polyacrylamide Gel; D020745:Genome, Archaeal; D006358:Hot Temperature; D008954:Models, Biological; D010084:Oxidation-Reduction; D010957:Plasmids / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D048229:Sulfolobus solfataricus / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000737:chemistry* / Q000502:physiology; D013997:Time Factors
chemical_list: D004220:Disulfides; D011994:Recombinant Proteins; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase