Thioredoxin, structural determination

Protein structure determinations have identified several examples of one domain inserted within another. One example is the E. coli DsbA protein, which catalyzes the formation of disulfide bonds in the periplasm. The enzyme consists of two domains a thioredoxin-like domain that contains the active site, and an inserted helical domain similar to the C-terminal domain of thermolysins (Martin et al., 1993). The inserted domain forms a cap over the active site, suggesting that it plays a role in binding to partially folded polypeptide chains before oxidation of... 

LeMaster, D.M. Structural determinants of the catalytic reactivity of the buried cysteine of Escherichia coli thioredoxin. Biochemistry 1996, 35,14876-81. 

The solution structure of a thioredoxin from B. acidocaldarius (Topt = 60 °C) has been studied by NMR and compared with that of E. coli determined by X-ray analysis. It was found that the higher thermostability of the former is due to cumulative effects, the main factor being an increased number of ionic interactions cross-linking different secondary structural elements. Multidimensional heteronuclear NMR spectroscopy was also employed to characterize thioredoxin homologues found in the hyperthermophilic... 

The thioredoxins are small, heat-stable proteins the E. coli thioredoxin has been purified to homogeneity and its complete pr.mary structure has been determined 12). Reduced thioredoxin is a single polypeptide chain of 108 amino acids (molecular weight 11,657) and contains two tryptophan and two cysteine residues. The N-terminal and the C-terminal amino acids are serine and alanine, respectively the amino acid sequence in the vicinity of the cysteines is as follows ... 

Because of its dithiol/disulphide exchange activity, thioredoxin determines the oxidation state of protein thiols. This small ( 12 kDa) protein is evo-lutionarily conserved between prokaryotes and eukaryotes from yeast to plants and animals. A characteristic feature of most thioredoxins is the presence of a conserved catalytic site Trp-Cys-Gly-Pro-Cys-Lys in a protrusion of the three-dimensional structure of the protein. The two cysteine residues of the site can be reversibly oxidies to form a disulphide bridge and, thereafter, ne re-... 

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