2l6d

Publication Abstract from PubMed

Cytoplasmic desulfothioredoxin (Dtrx) from the anaerobe Desulfovibrio vulgaris Hildenborough has been identified as a new member of the thiol disulfide oxidoreductase family. The active site of Dtrx contains a particular consensus sequence, CPHC, never seen in the cytoplasmic thioredoxins and generally found in periplasmic oxidases. Unlike canonical thioredoxins (Trx), Dtrx does not present any disulfide reductase activity but it presents instead an unusual disulfide isomerase activity. We have used NMR spectroscopy to gain insights into the structure and the catalytic mechanism of this unusual Dtrx. The redox potential of Dtrx (-181 mV) is significantly less reducing than that of canonical Trx. A pH dependence study allowed the determination of the pKa of all protonable residues, including the cysteine and histidine residues. Thus, the pKa for the thiol group of C31 and C34 is 4.8 and 11.3, respectively. The H33 pKa value, experimentally determined for the first time, differs notably as a function of the redox states, 7.2 for the reduced state and 4.6 for the oxidized state. These data suggest an important role of H33 in the molecular mechanism of Dtrx catalysis which is confirmed by the properties of mutant DtrxH33G protein. The NMR structure of Dtrx shows a different charge repartition compared to canonical Trx. The results presented are likely indicative of the involvement of this protein in the catalysis of substrates specific of the anaerobe cytoplasm of DvH. The study of Dtrx is an important step toward revealing the molecular details of the thiol-disulfide oxidoreductase catalytic mechanism.

Structural and mechanistic insights into an unusual thiol disulfide oxidoreductase.,Garcin EB, Bornet O, Elantak L, Vita N, Pieulle L, Guerlesquin F, Sebban-Kreuzer C J Biol Chem. 2011 Nov 28. PMID:22128175^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.