Thioredoxin homology

Witte S, Villalba M, Bi K, Liu Y, Isakov N, Altman A. Inhibition of the c-Jun N-terminal kinase/AP-1 and NF-kappaB pathways by PICOT, a novel protein kinase C-interacting protein with a thioredoxin homology domain. J Biol Chem 2000 275 1902-1909. 

The C-terminal domain of phosducin is a five-stranded mixed p sheet with a helices on both sides, similar to the thioredoxin fold of disulfide iso-merase DsbA described in Chapter 6. Despite significant sequence homology to thioredoxin, the phosducin domain, unlike other members of this family. 

Some bacteriophage encode their own DNA polymerases. However, they usually rely on the host cell to provide accessory proteins. The sequence of the DNA polymerase from phage T7 is closely homologous to that of the Klenow fragment and the 3D structures are similar. The 80-kDa T7 polymerase requires the 12-kDa thioredoxin from the host cell as an additional subunit. It has been genetically engineered to improve its usefulness in DNA sequencing 278... 

The amino acid sequence of the protein, which can be inferred from the published cDNA sequence (Edman et ai, 1985), reveals that each PDI polyjjeptide contains two domains that are closely homologous to thioredoxin. This enzyme has been characterized in detail (Holmgren, 1985) and it has been shown that the cysteine residues in the sequence WCGPCK (residues 31-36) act as the reactive dithiol. Chemical modification studies have shown that the enzyme, like PDI, is inactivated by alkylation at neutral pH, and that only Cys-32 is alkylated (Kallis and... 

In 1996, Tamura and Stadtman showed that thioredoxin reductase from mammalia-in contrast to the bacterial homologs-is a selenoprotein, and that selenocysteine is the penultimate C-terminal amino acid residue. Selenium-containing isoenzymes, which are tissue specific, have later on been characterized biochemically, or the existence of such isoforms was suggested by in-sihco methods. The substrate of thioredoxin reductase is thioredoxin, which is the key regulator of the redox status within cells. Thioredoxin catalyzes thiol-disulfide exchange reactions in proteins and peptides it is involved as redox mediator in the... 

Tagaya, Y., Maeda, Y., Mitsui, A., Kondo, N., Matsui, H., Hamuro, J., Brown, N., Arai, K., Yokota, T., Wakasugi, H., and et al. (1989). ATL-derived factor (ADF), an IL-2 receptor/Tac inducer homologous to thioredoxin possible involvement of dithiol-reduction in the IL-2 receptor induction. EMBO J 8,757-64. 

The thioredoxin reductases are highly specific for their thioredoxin substrate. For instance, yeast thioredoxin reductase is specific for the reduction of the homologous thioredoxins and does not interact with thioredoxins from E. coli or from T4-infected E. coli. Furthermore E. coli thioredoxin reductase does not use the thioredoxins from Novikoff hepatoma, yeast, and L. leichmannii. 

The endoplasmic reticulum PDl, which catalyzes the reduction, oxidation, and reshufSing of protein disulfides in eukaryotes, is a homodimer of two 57 kDa subunits. Each subunit contains two functional domains with significant sequence homology to Escherichia coli thioredoxin. The functional equivalent of PDI in prokaryotes, DsbA, is a periplasmic, monomeric protein characterized by a low similarity to E. coli thioredoxin with the active site sequence motif CPHC. ... 

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. 

As observed before with pig adrenodoxin. HTR is able to promote the light activation of NADP- MDH. Replacing the plant type thioredoxin m by an animal thioredoxin results in a deaeased NADP- MDH light activation (30% compared to an homologous system). Moreover, the optimal concentration (around 40 pM) is higher than the one of spinach thioredoxin m (around 10 (lM). 

---