Characterisation of the components of the thioredoxin system in the archaeon Sulfolobus solfataricus
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Updated: Jul 5, 2026

Adaptation at the Extremes of Life: Experimental Evolution with the Extremophile Archaeon Sulfolobus acidocaldarius
Published on: June 14, 2024
Pasquale Grimaldi1, Maria Rosaria Ruocco, Maria Angela Lanzotti
1Dipartimento di Scienze Farmacobiologiche, Università di Catanzaro Magna Graecia, Complesso Ninì Barbieri, 88021, Roccelletta di Borgia, Catanzaro, Italy.
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.
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