Structure and stability of a thioredoxin reductase from Sulfolobus solfataricus: A thermostable protein with two functions(840 views) Ruggiero A, Masullo M, Ruocco MR, Grimaldi P, Lanzotti MA, Arcari P, Zagari A, Vitagliano L
Keywords: Archaea, Cofactor Binding, Nadh Oxidase, Oxidoreductase, Protein Function And Stability, Reduced Nicotinamide Adenine Dinucleotide Dehydrogenase, Thioredoxin Reductase, Article, Circular Dichroism, Crystal Structure, Denaturation, Enzyme Isolation, Enzyme Structure, Priority Journal, Protein Analysis, Protein Stability, Protein Structure, Sulfolobus Solfataricus, Thermostability, Wild Type, Amino Acid Sequence, Binding Sites, Disulfides, Enzyme Stability, Flavin-Adenine Dinucleotide, Models, Molecular, Molecular Sequence Data, Sequence Alignment, Thioredoxin-Disulfide Reductase,
Affiliations: *** IBB - CNR ***
Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Napoli, Italy
Dipartimento di Scienze Farmacobiologiche, Università degli Studi Magna Graecia di Catanzaro, Roccelletta di Borgia, I-88021 Catanzaro, Italy
Dipartimento di Biochimica e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Via S. Pansini 5, I-80131 Napoli, Italy
Dipartimento delle Scienze Biologiche, Sezione di Biostrutture, Università degli Studi di Napoli Federico II, Via Mezzocannone 16, I-80134 Napoli, Italy
CEINGE Biotecnologie Avanzate s.c.a r.l., Via Comunale Margherita 482, I-80145 Napoli, Italy
References: Not available.
Structure and stability of a thioredoxin reductase from Sulfolobus solfataricus: A thermostable protein with two functions
Recent investigations have demonstrated that disulfide bridges may play a crucial role in the stabilization of proteins in hyperthermophilic organisms. A major role in the process of disulfide formation is played by ubiquitous proteins belonging to the thioredoxin superfamily, which includes thioredoxins (Trx), thioredoxin reductases (TrxR), and disulfide oxidases/isomerases (PDO/PDI). Here we report a characterization of the structure and stability of the TrxR (SsTrxRB3) isolated from the archaeon Sulfolobus solfataricus. This protein is particularly interesting since it is able to process different substrates (Trxs and PDO) and it is endowed with an additional NADH oxidase activity. The crystal structure of the wild-type enzyme, of its complex with NADP and of the C147A mutant provides interesting clues on the enzyme function. In contrast to what is observed for class II TrxRs, in the structure of the oxidized enzyme, the FAD binding site is occupied by a partially disordered NAD molecule. In the active site of the C147A mutant, which exhibits a marginal NADH oxidase activity, the FAD is canonically bound to the enzyme. Molecular modeling indicates that a FAD molecule can be accommodated in the site of the reduced SsTrxRB3. Depending on the oxidation state, SsTrxRB3 can bind a different cofactor in its active site. This peculiar feature has been related to its dual activity. Denaturation experiments followed by circular dichroism indicate that electrostatic interactions play an important role in the stabilization of this thermostable protein. The analysis of the enzyme 3D-structure has also provided insights into the bases of SsTrxRB3 stability. (C) 2008 Elsevier B.V. All rights reserved.
Structure and stability of a thioredoxin reductase from Sulfolobus solfataricus: A thermostable protein with two functions