Article (Scientific journals)
The Zinc Center Influences the Redox and Thermodynamic Properties of Escherichia coli Thioredoxin 2
El Hajjaji, Hayat; Dumoulin, Mireille; Matagne, André et al.
2009In Journal of Molecular Biology, 386 (1), p. 60-71
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Keywords :
oxidative stress; thioredoxin; zinc; disulfide bonds; cysteine; Protein stability; Thermodynamics; Folding
Abstract :
[en] Thioredoxins are small, ubiquitous redox enzymes that reduce protein disulfide bonds by using a pair of cysteine residues present in a strictly conserved WCGPC catalytic motif. The Escherichia coli cytoplasm contains two thioredoxins, Trx1 and Trx2. Trx2 is special because it is induced under oxidative stress conditions and it has an additional N-terminal zinc-binding domain. We have determined the redox potential of Trx2, the pKa of the active site nucleophilic cysteine, as well as the stability of the oxidized and reduced form of the protein. Trx2 is more oxidizing than Trx1 (–221 mV versus –284 mV, respectively), which is in good agreement with the decreased value of the pKa of the nucleophilic cysteine (5.1 versus 7.1, respectively). The difference in stability between the oxidized and reduced forms of an oxidoreductase is the driving force to reduce substrate proteins. This difference is smaller for Trx2 (ΔΔG°H2O = 9 kJ/mol and ΔTm = 7. 4 °C) than for Trx1 (ΔΔG°H2O = 15 kJ/mol and ΔTm = 13 °C). Altogether, our data indicate that Trx2 is a significantly less reducing enzyme than Trx1, which suggests that Trx2 has a distinctive function. We disrupted the zinc center by mutating the four Zn2+-binding cysteines to serine. This mutant has a more reducing redox potential (–254 mV) and the pKa of its nucleophilic cysteine shifts from 5.1 to 7.1. The removal of Zn2+ also decreases the overall stability of the reduced and oxidized forms by 3.2 kJ/mol and 5.8 kJ/mol, respectively. In conclusion, our data show that the Zn2+-center of Trx2 fine-tunes the properties of this unique thioredoxin.
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
El Hajjaji, Hayat;  de Duve Institute, Université catholique de Louvain, B-1200 Brussels, Belgium
Dumoulin, Mireille  ;  Université de Liège - ULiège > Département des sciences de la vie > Enzymologie et repliement des protéines, Centre d'Ingénierie des Protéines
Matagne, André  ;  Université de Liège - ULiège > Département des sciences de la vie > Enzymologie et repliement des protéines, Centre d'Ingénierie des Protéines
Colau, Didier;  Ludwig Institute for Cancer Research, Université catholique de Louvain, B-1200 Brussels, Belgium
Messens, Joris;  Department of Molecular and Cellular Interactions, VIB, Structural Biology Brussels, Vrije Universiteit Brussel, B-1050 Brussels, Belgium
Collet, Jean-Francois;  de Duve Institute, Université catholique de Louvain, B-1200 Brussels, Belgium
Language :
English
Title :
The Zinc Center Influences the Redox and Thermodynamic Properties of Escherichia coli Thioredoxin 2
Publication date :
13 February 2009
Journal title :
Journal of Molecular Biology
ISSN :
0022-2836
eISSN :
1089-8638
Publisher :
Academic Press, London, United Kingdom
Volume :
386
Issue :
1
Pages :
60-71
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 26 May 2009

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