Glutaredoxins oxidoreductases

Aslund, E, Bemdt, K.D., Holmgren, A. Redox potentials of glutaredoxins and other thiol-disulfide oxidoreductases of the thioredoxin superfamily determined by direct protein-protein redox equilibria. J Biol Chem 272(49), 30780-30786 (1997)... 

Both thioredoxin and glutaredoxin are members of a larger group of thiol disulfide oxidoreductases which are found in all known organisms. In E. coli there are one thioredoxin, three different glutaredoxins,h/t and the periplasmic protein disulfide... 

Little information is availble on protein disulfide oxidoreductases in Archaea. A glut iredoxin-like protein, isolated from Methanobacterium thermoautotroph-icum, was shown to have a molecular mass of 9 kDa, and a low sequence identity (<20%) to known glutaredoxin, and not to function as glutaredoxin-dependent enzyme. 

A highly thermostable protein disulfide oxidoreductase was first isolated from Sulfolobus solfataricus. From its ability to catalyze the reduction of insulin disulfides in the presence of dithiothreitol (DTT), the protein was considered a thioredoxin. The protein showed an unusually high molecular mass of 25 kDa and from amino acid composition analysis contained four cysteine residues. A homologous protein was subsequently purified from Pyrococcus furiosus. From its amino acid sequence, which showed two distinct CXXC motifs, and from its thioltransferase activity the protein was considered to be a glutaredoxin-like protein. 

Unlike thioredoxin, glutaredoxin, and DsbA, which possess only one thiore-doxin-like motif, P/PDO is the first protein disulfide oxidoreductase whose three-dimensional structure has been shown to contain two thioredoxin fold motifs with two active sites. Thus, P/PDO shows structural resemblance to PDI and PDI-like protein s. This structural feature suggests that P/PDO is probably not just a simple protein disulfide reductant like thioredoxin as described previously. It may belong to the growing family of PDI-like proteins. From a structural point of view, P/PDO may represent the simplest form of PDI. 

Figure 3. For the B. subtilis genome, the distribution of Blocks scores [236, 237] for the thioredoxin block and glutaredoxin blocks are presented. FFF indicates that the threaded structure satisfies the disulfide oxidoreductase active site descriptor, CP indicates that the sequence identified by threading and FFF satisfies the conservation profile, and indicates that there is just one sequence so that a CP analysis cannot be done.

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