Tryptophan residues thioredoxin

The procedure outlined below, based upon the description of Previero et al. (1967b) has been used successfully, with minor variations for the selective modification of tryptophan residues in lysozyme (Previero et al. 1967b), trypsin (Coletti-Previero et al. 1969), cytochrome c (Aviram and Schejter 1971), and thioredoxin (Holmgren 1972). 

Thioredoxin from yeast has been obtained in two forms (I and II) of which thioredoxin II has been purified to homogeneity (43). Both yeast thioredoxins are able to serve as hydrogen donors for the ribonucleotide reductase from E. coli. The molecular weight (12,600) of thioredoxin II is similar to that of thioredoxin from E. coli. Although both yeast thioredoxins contain only one tryptophan residue and although their amino acid compositions differ markedly from that of E. coli thioredoxin, the amino acid sequences around the disulfide bridge of these three thioredoxins are identical ... 

A thioredoxin has also been partially purified from L. leichtnannii (39). Although this thioredoxin is similar in size (MW approximately 12,000) to the E. coli thioredoxin, it is not able to function as a substrate for the E. coli thioredoxin reductase. More recently thioredoxins have been purified to homogeneity from rat Novikoff ascites hepatoma (127) and from calf liver (45). The properties of these two thioredoxins are quite similar (MW 11,400 and 12,000 respectively). The amino acid compositions however, are different. For instance the Novikoff tumor thioredoxin contains six half-cysteine residues, whereas calf liver thioredoxin has only four. Both these thioredoxins have a tendency to aggregate in the oxidized form. This aggregation is probably due to mixed sulfide formation between the additional sulfhydryl groups. Like yeast thioredoxin II, calf liver thioredoxin contains only one tryptophan residue unfortunately the tryptophan content of Novikoff tumor thioredoxin was not determined. 

Holmgren, A. Reversible Chemical Modification of the Tryptophan Residues of Thioredoxin from Escherichia coli B. Eur. J. Biochem. 26, 528-534 (1972). 

Effects of Oxidation of Tryptophan Residues in Thioredoxin from Escherichia coli by N-Bromosuccinimide. J. Biol. Chem. 248, 4106-4111 (1973). 

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 ... 

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