Purification and characterization of Taenia crassiceps cysticerci thioredoxin: insight into thioredoxin-glutathione-reductase (TGR) substrate recognition

• A simple purification method for T. crassiceps thioredoxin (TcTrx) was developed.
• Oxidized and reduced forms of the TcTrx monomer were identified in native PAGE.
• A negative patch identified in TcTrx sequence could influence TGR recognition.

Thioredoxin (Trx) is an oxidoreductase central to redox homeostasis in cells and is involved in the regulation of protein activity through thiol/disulfide exchanges. Based on these facts, our goal was to purify and characterize cytosolic thioredoxin from Taenia crassiceps cysticerci, as well as to study its behavior as a substrate of thioredoxin-glutathione reductase (TGR). The enzyme was purified > 133-fold with a total yield of 9.7%. A molecular mass of 11.7 kDa and a pI of 4.84 were measured.Native electrophoresis was used to identify the oxidized and reduced forms of the monomer as well as the presence of a homodimer. In addition to the catalytic site cysteines, cysticerci thioredoxin contains Cys28 and Cys65 residues conserved in previously sequenced cestode thioredoxins. The following kinetic parameters were obtained for the substrate of TGR: a Km of 3.1 μM, a kcat of 10 s− 1 and a catalytic efficiency of 3.2 × 106 M− 1 s− 1. The negative patch around the α3-helix of Trx is involved in the interaction with TGR and suggests variable specificity and catalytic efficiency of the reductase toward thioredoxins of different origins.

Figure optionsDownload as PowerPoint slide