Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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The cytosolic thioredoxin h (112 amino acids, 11.8 kDa) cDNA from the eukaryotic green alga Chlamydomonas reinhardtii has been over-expressed in Escherichia coli and the protein was uniformly labelled with 13C and 15N. For the backbone resonance assignments (HN, N, C alpha, CO and H alpha) we used a new set of two-dimensional triple-resonance correlation experiments [Simorre, J.-P., Brutscher, B., Caffrey, M. S. & Marion, D. (1994) J. Biomol. NMR 4, 325-333; Brutscher, B., Simorre, J.-P., Caffrey, M. S. & Marion, D. (1994) J. Magn. Reson. B 105, 77-82] and the new computer assignment protocol ALPS (Assignment for Labelled Protein Spectra) developed in our laboratory [Morelle, N., Brutscher, B., Simorre, J.-P. & Marion, D. (1995) J. Biomol. NMR 5, 154-160]. The assignment was extended to the side chains using three-dimensional HC(C)H-TOCSY correlation experiments together with a set of regular two-dimensional proton spectra. The secondary and super-secondary structures were deduced from the C alpha chemical-shift differences to the random-coil values, the measure of the exchange rates of slow-exchanging amide protons using 15N-HSQC spectroscopy, and the assignment of medium and long-range NOEs. The oxidized C. reinhardtii thioredoxin h is based on an open alpha/beta motif consisting of a five-stranded beta-sheet surrounded by four helices in a manner similar to the bacterial E. coli thioredoxin [Katti, S. K., LeMaster, D. M. & Eklund, H. (1990) J. Mol. Biol. 212, 167-184; Jeng, M.-F., Campbell, A. P., Begley, T., Holmgren, A., Case, D. A., Wright, P. E. & Dyson, H. J. (1994) Structure 2, 853-868] and the human thioredoxin [Qin, J., Clore, G. M. & Gronenborn, A. M. (1994) Structure 2, 503-522] for which C. reinhardtii thioredoxin h shares 32 and 44 sequence identities, respectively. From the analysis of the secondary structure characteristics, the C. reinhardtii thioredoxin h is closer to the human thioredoxin structure than to the bacterial thioredoxin structure. Conversely, the latter would share several structural features with the previously reported [Lancelin, J.-M., Stein, M. & Jacquot, J.-P. (1993) J. Biochem. (Tokyo) 114, 421-431] highly thermostable chloroplast C. reinhardtii thioredoxin m that is involved in the thiol-redox enzymic control of photosynthetic intermediate carbon metabolism.
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PMID:1H, 13C, 15N-NMR resonance assignments of oxidized thioredoxin h from the eukaryotic green alga Chlamydomonas reinhardtii using new methods based on two-dimensional triple-resonance NMR spectroscopy and computer-assisted backbone assignment. 774 70

Specific polyclonal antibodies towards the oxidized form of bovine thioredoxin reductase (TR) have been obtained in rabbits, and purified. The antigenicity was lost upon reduction of TR by NADPH indicating a large conformational change upon reduction of the redox-active disulfide in the enzyme. The antibodies did not cross-react with other bovine NADPH-dependent dehydrogenases. No reactivity was observed with TR from bacteria, yeast or rat and only a slight reaction was obtained with TR from horse. Immunoaffinity purified anti-thioredoxin and anti-glutaredoxin antibodies were used to develop competitive indirect ELISA assays that were validated giving very good linearity, reproducibility, sensitivity and parallelism. The glutaredoxin (Grx) immunoassay is the first quantitative method described to measure the protein. When applied to a battery of calf tissues the contents of Grx varied from 7 to 120 micrograms per gram of fresh tissue. Skeletal and heart muscles gave the lowest values and spleen and salivary glands the highest. However, skeletal muscle showed the highest gluthathione-hydroxyethyl disulfide oxidoreductase specific activity.
Comp Biochem Physiol B Biochem Mol Biol 1995 May
PMID:Characterization of mammalian thioredoxin reductase, thioredoxin and glutaredoxin by immunochemical methods. 774 33

The disulphide active sites of thioredoxin and DsbA are known to possess a high degree of structural homology. However, DsbA is a much stronger oxidant than thioredoxin. The redox potential difference between DsbA and thioredoxin has been measured to be 160 mV, equivalent to a shift of 15.4 kJ/mol in the reduced/oxidised equilibrium. Electrostatics calculations have been used to study the relative stabilities of the reduced forms of the two proteins. Model calculations suggest that much of the redox potential difference between DsbA and thioredoxin arises form altered stabilisation of the exposed and ionised thiolates of the reduced forms, supporting suggestions previously made on the basis of experimental studies. The calculations have been used to construct a molecular model for the difference in thiolate stabilisation. Although specific interactions, such as thiolate-NH 35 (thioredoxin)/33 (DsbA), provide substantial stabilisation in each reduced protein, the difference between thioredoxin and DsbA is predicted to reside in several side-chain and main-chain groups acting in concert. Residues H32 and Q97 in DsbA are predicted to contribute, along with substantial regions of the polypeptide backbone in the protein domain which is common to DsbA and thioredoxin. Increased thiolate stabilisation by the peptide dipoles is suggested to arise from altered main-chain disposition, and the effect of the additional protein domain of DsbA on the electric field. Peptide dipoles in a region of about 20 residues close to the active site disulphide are predicted to contribute significantly to the redox potential difference.
J Mol Biol 1995 Jun 02
PMID:A molecular model for the redox potential difference between thioredoxin and DsbA, based on electrostatics calculations. 778

Screening of a Drosophila genomic DNA library at reduced stringency hybridization conditions using a rat PLC alpha cDNA probe yielded a gene which encodes a member of the protein disulfide isomerase/PLC alpha family. The gene has been localized to band 74C on the left arm of the third chromosome and has been designated dpdi. Northern analysis shows that the dpdi gene encodes a transcript that is 2.3 kb in length and is present throughout development as well as in both heads and bodies of adults. The deduced dpdi protein is 496 amino acids in length and contains two domains exhibiting high similarity to thioredoxin, two regions that are similar to the hormone binding domain of human estrogen receptor, and a sequence of four amino acids (KDEL) at the C-terminus which has been described by others as being responsible for retention of proteins in the endoplasmic reticulum. Overall, dpdi contains a higher similarity to rat protein disulfide isomerase (53% identical) than to rat PLC alpha (30% identical). However, it is unclear whether dpdi functions in vivo as a PDI or as a PLC, or both. Drosophila, with its well characterized genetics and the ability to generate mutants in a gene that has been cloned, provides an excellent system in which to resolve this issue.
Insect Biochem Mol Biol 1995 May
PMID:A Drosophila gene that encodes a member of the protein disulfide isomerase/phospholipase C-alpha family. 778 47

The recently cloned cDNA for pea chloroplast thioredoxin f was used to produce, by PCR, a fragment coding for a protein lacking the transit peptide. This cDNA fragment was subcloned into a pET expression vector and used to transform E. coli cells. After induction with IPTG the transformed cells produce the protein, mainly in the soluble fraction of the broken cells. The recombinant thioredoxin f has been purified and used to raise antibodies and analysed for activity. The antibodies appear to be specific towards thioredoxin f and do not recognize other types of thioredoxin. The recombinant protein could activate two chloroplastic enzymes, namely NADP-dependent malate dehydrogenase (NADP-MDH) and fructose 1,6-bisphosphatase (FBPase), both using dithiothreitol as a chemical reductant and in a light-reconstituted/thylakoid assay. Recombinant pea thioredoxin f turned out to be an excellent catalyst for NADP-MDH activation, being the more efficient than a recombinant m-type thioredoxin of Chlamydomonas reinhardtii and the thioredoxin of E. coli. At the concentrations of thioredoxin used in the target enzyme activation assays only the recombinant thioredoxin f activated the FBPase.
Plant Mol Biol 1994 Oct
PMID:Purification and characterization of pea thioredoxin f expressed in Escherichia coli. 794 72

A gene encoding a thioredoxin protein was identified in the chloroplast genome of the rhodophyte Porphyra yezoensis. The P. yezoensis trxA gene contains 324 bp and is transcribed into a 0.7 kb messenger RNA. Analysis of the transcription start site demonstrates that canonical chloroplast -10 and -35 sequences are not present. The deduced amino acid sequence of the thioredoxin gene from the red algae has the greatest similarity to type m thioredoxins, providing strong support for the hypothesis that type m thioredoxins in photosynthetic eukaryotes originated from an engulfed bacterial endosymbiont. Hybridization analysis of nuclear and chloroplast DNAs from several members of the phyla Chromophyta and Rhodophyta using P. yezoensis DNA as a probe demonstrated strong hybridization to the chloroplast and nuclear genomes of Griffithsia pacifica and a weak cross-hybridization to the chromophyte P. foliaceum. The G. pacifica chloroplast gene has a 66% identity with the P. yezoensis DNA, contains conserved active site amino acid residues, but lacks a methionine start codon.
Plant Mol Biol 1994 Apr
PMID:Chloroplast encoded thioredoxin genes in the red algae Porphyra yezoensis and Griffithsia pacifica: evolutionary implications. 800 93

Resistance to arsenate conferred on Escherichia coli by the ars operon of plasmid R773 requires both the product of the arsC gene and reduction of arsenate to arsenite. A genetic analysis was performed to identify the source of reducing potential in vivo. In addition to the ars genes, arsenate resistance required the products of the gor gene for glutathione reductase and the gshA and gshB genes for glutathione synthesis. Mutations in the trx and grx genes for thioredoxin and glutaredoxin, respectively, had no effect on arsenate resistance. Although resistance required the arsC gene, the rate of reduction of arsenate to arsenite was nearly the same in cells lacking the ars operon. In strains deficient in glutathione biosynthesis this endogenous reduction was greatly diminished, and cells exhibited increased sensitivity to arsenate. When glutathione was supplied exogenously to such mutants, resistance was restored only to cells expressing the ars operon, and only such cells had detectable arsenate reduction after addition of glutathione. Since ArsC-catalysed reduction of arsenate provides high level resistance, physical coupling of the ArsC reaction to efflux of the resulting arsenite is hypothesised.
Mol Microbiol 1994 Apr
PMID:Arsenate reduction mediated by the plasmid-encoded ArsC protein is coupled to glutathione. 805 54

The crystal structures of three forms of Escherichia coli thioredoxin reductase have been refined: the oxidized form of the wild-type enzyme at 2.1 A resolution, a variant containing a cysteine to serine mutation at the active site (Cys138Ser) at 2.0 A resolution, and a complex of this variant with nicotinamide adenine dinucleotide phosphate (NADP+) at 2.3 A resolution. The enzyme mechanism involves the transfer of reducing equivalents from reduced nicotinamide adenine dinucleotide phosphate (NADPH) to a disulfide bond in the enzyme, via a flavin adenine dinucleotide (FAD). Thioredoxin reductase contains FAD and NADPH binding domains that are structurally similar to the corresponding domains of the related enzyme glutathione reductase. The relative orientation of these domains is, however, very different in the two enzymes: when the FAD domains of thioredoxin and glutathione reductases are superimposed, the NADPH domain of one is rotated by 66 degrees with respect to the other. The observed binding mode of NADP+ in thioredoxin reductase is non-productive in that the nicotinamide ring is more than 17 A from the flavin ring system. While in glutathione reductase the redox active disulfide is located in the FAD domain, in thioredoxin reductase it is in the NADPH domain and is part of a four-residue sequence (Cys-Ala-Thr-Cys) that is close in structure to the corresponding region of thioredoxin (Cys-Gly-Pro-Cys), with a root-mean-square deviation of 0.22 A for atoms in the disulfide bonded ring. There are no significant conformational differences between the structure of the wild-type enzyme and that of the Cys138Ser mutant, except that a disulfide bond is not present in the latter. The disulfide bond is positioned productively in this conformation of the enzyme, i.e. it stacks against the flavin ring system in a position that would facilitate its reduction by the flavin. However, the cysteine residues are relatively inaccessible for interaction with the substrate, thioredoxin. These results suggest that thioredoxin reductase must undergo conformational changes during enzyme catalysis. All three structures reported here are for the same conformation of the enzyme and no direct evidence is available as yet for such conformational changes. The simplest possibility is that the NADPH domain rotates between the conformation observed here and an orientation similar to that seen in glutathione reductase. This would alternately place the nicotinamide ring and the disulfide bond near the flavin ring, and expose the cysteine residues for reaction with thioredoxin in the hypothetical conformation.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1994 Feb 25
PMID:Crystal structure of Escherichia coli thioredoxin reductase refined at 2 A resolution. Implications for a large conformational change during catalysis. 811 95

Using a clone characterized in the course of a random sequencing programme of Arabidopsis thaliana, two cDNAs encoding plant type cytosolic NADPH-dependent thioredoxin reductase (NTR) have been isolated. Their sequence homology with Escherichia coli NRT (the only thioredoxin reductase of known primary structure) is about 45%. In addition, analysis of the sequence of the encoded polypeptide (333 amino acids) reveals that several motifs are conserved in the FAD, central and NADPH binding domains, suggesting a similar folding of the protein. Definitive proof that the clone ATTHIREDB indeed encodes NTR was obtained by expressing the recombinant protein in E. coli cells. It was observed that plant type NTR was strongly overproduced (about 10 mg homogeneous protein could be purified per liter of culture). The recombinant enzyme is homodimeric, each subunit containing an FAD prosthetic group. Recombinant plant type NTR is as effective as E. coli NTR in the DTNB (5,5'-dithiobis nitrobenzoic acid) reduction reaction, but its affinity for thioredoxin substrates was strikingly different. These results are discussed in relation to the primary structures of NADPH thioredoxin reductases.
J Mol Biol 1994 Jan 28
PMID:Arabidopsis thaliana NAPHP thioredoxin reductase. cDNA characterization and expression of the recombinant protein in Escherichia coli. 830

In this study we have examined several parameters that can be used for checking the consistency and accuracy of protein structures and molecular dynamics simulations. This is done by comparing: (1) three X-ray structures of oxidized Escherichia coli thioredoxin (Trx-S2); (2) 14 NMR structures of reduced E. coli thioredoxin (Trx-(SH)2); and (3) 30 different simulations, 15 of Trx-S2 and 15 of Trx-(SH)2. The energy, the agreement with NOE data, the root-mean-square deviation between structures, and the surface characteristics of all these structures are analyzed. The 30 simulations, four water simulations, 20 standard vacuum simulations and six alternative vacuum simulations, are examined with respect to mobility, temperature factors and aromatic side-chain mobility. It is shown that although vacuum simulations may reproduce some parameters, all the features of a water simulation cannot be reproduced in any of these simulations. Several of the parameters described above are shown to be good for discriminating between an accurate and an inaccurate simulation. It is also shown that 100 ps is too short a time to obtain statistically certain temperature factors and correlation functions of aromatic side-chain motions. The results also suggest that performing ten 100 ps simulations spans the conformation space better than one 1 ns simulation.
J Mol Biol 1993 Oct 20
PMID:How consistent are molecular dynamics simulations? Comparing structure and dynamics in reduced and oxidized Escherichia coli thioredoxin. 841 Nov 78


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