The primary structure of calf thymus glutaredoxin. Homology with the corresponding Escherichia coli protein but elongation at both ends and with an additional half-cystine/cysteine pair.

The primary structure of calf thymus glutaredoxin was determined by analysis of the [14C]carboxymethylated protein and the proteolytic fragments obtained by treatments with trypsin, chymotrypsin, CNBr and staphylococcal Glu-specific extracellular protease. The active center has the structure Cys-Pro-Tyr-Cys, with the redox-active cysteines/half-cystines located at positions 22 and 25 in the polypeptide chain. This active center is identical in amino acid sequence and similar in position to that of Escherichia coli glutaredoxin, suggesting this structure to be typical for glutaredoxins and distinguishing them from the distantly related thioredoxins. However, the two glutaredoxins also exhibit considerable differences. Calf thymus glutaredoxin is extended at both ends and has 31% overall residue identities with the corresponding E. coli protein. In contrast to the bacterial glutaredoxin, the calf thymus protein contains two additional half-cystines/cysteine residues at positions 74 and 78, which may be of regulatory significance.