Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protocols are described for the isolation from human placental extracts of a preparation which is active in the rosette inhibition assay by inducing an increased rosette inhibition titre. In this respect the preparation mimics the effects of pregnancy sera, an ability ascribed to the presence in these sera of a so-called 'early pregnancy factor' (EPF). In addition to this activity in the rosette inhibition assay, the preparation was also shown to modulate the expression of cell surface immunoglobulin on peripheral blood mononuclear cells. The polypeptide composition of the preparation was relatively simple, as revealed by SDS-PAGE. There was a major 12 kd polypeptide previously isolated in a rosette inhibition titre-active preparation from ovine placental extracts, and a small amount of 68 kd polypeptide. N-Terminal amino acid sequence analyses obtained after blotting onto polyvinylidene difluoride membranes identified the latter polypeptide as serum albumin and the major 12 kd polypeptide as human thioredoxin. Gel permeation analysis partially resolved activity expression away from the 12 kd polypeptide as activity expression was also found to be associated with low mol. wt material. It is concluded that EPF activity expression in pregnancy sera involves molecules related to and associated with thioredoxin.
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PMID:Isolation from human placental extracts of a preparation possessing 'early pregnancy factor' activity and identification of the polypeptide components. 195 57

The nucleotide sequence of the gene cysH from Escherichia coli K12 was determined. The open reading frame was 735 nucleotides in length; it was flanked by a repetitive palindromic sequence centred 36 nucleotides upstream of cysH and a terminator-like structure located 20 nucleotides downstream. CysH encoded a polypeptide of Mr 27927 consisting of 244 amino acids. The gene product was isolated as a homodimer exhibiting phospho-adenylylsulphate reductase (PAPS reductase) activity. The active enzyme was devoid of electron transferring cofactors and contained only one cysteine per subunit. Reduction of the enzyme by dithiols resulted in a shift of the apparent molecular weight from 44,000 to 62,000 without formation of an enzyme-thioredoxin complex.
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PMID:Characterisation of the gene cysH and of its product phospho-adenylylsulphate reductase from Escherichia coli. 200 73

1. The number of reactive thiol groups in mammalian liver protein disulphide-isomerase (PDI) in various conditions was investigated by alkylation with iodo[14C]acetate. 2. Both the native enzyme, as isolated, and the urea-denatured enzyme contained negligible reactive thiol groups; the enzyme reduced with dithiothreitol contained two groups reactive towards iodoacetic acid at pH 7.5, and up to five reactive groups were detectable in the reduced denatured enzyme. 3. Modification of the two reactive groups in the reduced native enzyme led to complete inactivation, and the relationship between the loss of activity and the extent of modification was approximately linear. 4. Inactivation of PDI by alkylation of the reduced enzyme followed pseudo-first-order kinetics; a plot of the pH-dependence of the second-order rate constant for inactivation indicated that the essential reactive groups had a pK of 6.7 and a limiting second-order rate constant at high pH of 11 M-1.s-1. 5. Since sequence data on PDI show the presence within the polypeptide of two regions closely similar to thioredoxin, the data strongly indicate that these regions are chemically and functionally equivalent to thioredoxin. 6. The activity of PDI in thiol/disulphide interchange derives from the presence of vicinal dithiol groups in which one thiol group of each pair has an unusually low pK and high nucleophilic reactivity at physiological pH.
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PMID:The reactivities and ionization properties of the active-site dithiol groups of mammalian protein disulphide-isomerase. 202 20

1. The redox properties of the active-site dithiol/disulphide groups of PDI were determined by equilibrating the enzyme with an excess of GSH + GSSG, rapidly alkylating the dithiol form of the enzyme to inactivate it irreversibly, and determining the proportion of the disulphide form by measuring the residual activity under standard conditions. 2. The extent of reduction varied with the applied redox potential; to a first approximation, the data fitted a model in which all the enzyme dithiol/disulphide groups are independent and equivalent and the equilibrium constant between these sites and the GSH/GSSG redox couple is 42 microM at pH 7.5. 3. The standard redox potential for PDI active-site dithiol/disulphide couples was calculated from this result and found to be -0.11 V; hence PDI is a stronger oxidant and weaker reductant than GSH, nicotinamide cofactors, thioredoxin and dithiothreitol. 4. The redox equilibrium data for PDI with the GSH/GSSG redox couple showed sigmoidal deviations from linearity. The sigmoidicity could be modelled closely by assuming a Hill coefficient of 1.5. 5. This evidence of co-operative interactions between the four active sites in a PDI dimer was extended by studying the reaction between PDI and homobifunctional alkylating agents with various lengths between the reactive groups. A species whose electrophoretic mobility suggested it contained an intrachain cross-link was observed in all cases, whereas there was no evidence for cross-linking between the chains of the PDI homodimer. Most effective cross-linking was achieved with reagents containing five or more methylene spacer groups, implying a minimum distance of 1.6 nm (16 A) between the active-site reactive groups within the two thioredoxin-like domains of the PDI polypeptide.
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PMID:Redox properties and cross-linking of the dithiol/disulphide active sites of mammalian protein disulphide-isomerase. 202 21

A second thioredoxin, Ch1, distinct from the one recently reported [Decottignies, P., Schmitter, J.M., Jacquot, J. P., Dutka, S., Picaud, A. & Gadal, P. (1990) Arch, Biochem. Biophys. 280, 112-121] has been purified from the green alga, Chlamydomonas reinhardtii, and its functional and structural properties investigated. Its activity in various enzymatic assays has been compared with the activities of different plant thioredoxins (Ch2 from C. reinhardtii and spinach m and f). Ch1 cannot serve as a substrate for Escherichia coli thioredoxin reductase, but can be reduced by spinach ferredoxin-thioredoxin reductase. It is less efficient than its spinach counterpart in the activation of corn leaf NADP-dependent malate dehydrogenase by light or dithiothreitol, and it only activates spinach fructose-1,6-bisphosphatase at very high concentrations. The complete primary structure of C. reinhardtii thioredoxin Ch1 was determined by automated Edman degradation of the intact protein and of peptides derived from trypsin, chymotrypsin and Staphylococcus aureus V8 protease digestions. When needed, peptide masses were verified by plasma desorption mass spectrometry. Ch1 consists of a polypeptide of 111 amino acids (11634 Da) and contains the well-conserved active site sequence Trp-Cys-Gly-Pro-Cys. Compared to thioredoxins from other sources, the algal thioredoxin Ch1 displays few sequence similarities with all the thioredoxins sequenced so far. Preliminary evidence indicates that Ch1 may be an h-type thioredoxin.
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PMID:Characterization and primary structure of a second thioredoxin from the green alga, Chlamydomonas reinhardtii. 204 Mar 9

The amino acid sequence of the spinach chloroplast fructose-1,6-bisphosphatase (FBPase) subunit has been determined. Placement of the 358 residues in the polypeptide chain was based on automated Edman degradation of the intact protein and of peptides obtained by enzymatic or chemical cleavage. The sequence of spinach chloroplast FBPase shows clear homology (ca. 40%) to gluconeogenic (mammalian, yeast, and Escherichia coli) fructose-1,6-bisphosphatases and 80% homology with the wheat chloroplast enzyme. The two chloroplast enzymes show near the middle of the structure a unique sequence insert probably involved in light-dependent regulation of the chloroplast FBPase enzyme activity. This sequence insert contains two cysteines separated by only 4 amino acid residues, a characteristic feature of some enzymes containing redox-active cysteines. The recent X-ray crystallographic resolution of pig kidney FBPase (H. Ke, C. M. Thorpe, B. A. Seaton, F. Marcus, and W. N. Lipscomb, 1989, Proc. Natl. Acad. Sci. USA 86, 1475-1479) has allowed the discussion of the amino acid sequence of spinach chloroplast FBPase in structural terms. It is to be noted that most of pig kidney FBPase residues shown to be either at (or close to) the sugar bisphosphate binding site or located at the negatively charged metal binding pocket are conserved in the chloroplast enzyme. The unique chloroplast FBPase insert presumably involved in light-dependent activation of the enzyme via a thioredoxin-linked mechanism can be accommodated in the surface of the FBPase molecule.
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PMID:Amino acid sequence of spinach chloroplast fructose-1,6-bisphosphatase. 215 55

Two thioredoxins (named Ch1 and Ch2 in reference to their elution pattern on an anion-exchange column) have been purified to homogeneity from the green alga, Chlamydomonas reinhardtii. In this paper, we described the properties and the sequence of the most abundant form, Ch2. Its activity in various enzymatic assays has been compared with those of Escherichia coli and spinach thioredoxins. C. reinhardtii thioredoxin Ch2 can serve as a substrate for E. coli thioredoxin reductase with a lower efficiency when compared to the homologous system. In the presence of dithiothreitol (DTT), the protein is able to catalyze the reduction of porcine insulin. Thioredoxin Ch2 is as efficient as its spinach counterpart in the DTT or light activation of corn NADP-malate dehydrogenase, but it only activates spinach fructose-1, 6-bisphosphatase at very high concentrations. The complete primary structure of the C. reinhardtii thioredoxin Ch2 was determined by automated Edman degradation of the intact protein and of peptides derived from trypsin, chymotrypsin, clostripain, and SV8 protease digestions. It consists of a polypeptide of 106 amino acids (MW 11,808) and contains the well-conserved active site sequence Trp-Cys-Gly-Pro-Cys. The sequence of the algal thioredoxin Ch2 has been compared to that of thioredoxins from other sources and has the greatest similarity (67%) with the thioredoxin from Anabaena 7119.
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PMID:Purification, characterization, and complete amino acid sequence of a thioredoxin from a green alga, Chlamydomonas reinhardtii. 219 28

The three-dimensional structure of a protein is governed by the thermodynamical principle established experimentally by Anfinsen, Isemura, and others. The rapidity of the folding process is another important key phenomenon. With these basics in mind an island model is proposed which requires a restricted folding pathway. A physicochemical method of the prediction of alpha-helices and beta-strands is also discussed. By virtue of the long-range hydrophobic interaction and the specific interactions between hydrophobic residues which are determined by the basic idea underlying the island model, one can fold the polypeptide chain into a tertiary structure upon determination of the secondary structures. Several examples of folding are presented. In myoglobin the heme group must be considered to reach the correct final tertiary structure. In lysozyme and phospholipase, the disulfide bondings are necessary to fasten the polypeptide chain. The selection of proper cysteine pairs among other possible ones is carried out by drawing the lampshades (locus of H atom of SH) of cysteines. In flavodoxin and thioredoxin the formation of parallel beta-structure from beta-strands is considered. The formations of antiparallel beta-structure in lysozyme and phospholipase are also discussed.
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PMID:Principles of protein architecture. 269 41

The primary structure of thioredoxin f from spinach chloroplasts was determined by standard amino acid sequencing and furthermore by sequencing the corresponding nuclear genome region. The protein, with a calculated molecular mass of 12,564 Da and a molar absorption coefficient at 280 nm of 17,700 M-1 cm-1, consists of 113 residues and exhibits 24% residue identities with spinach chloroplast thioredoxin mb or Escherichia coli thioredoxin. A monospecific antibody elicited against thioredoxin f has been used to select recombinant phage from spinach cDNA libraries in lambda gt11. The inserts of positive clones were sequenced. They code for a polypeptide of 190 amino acids, composed of the thioredoxin f sequence (113 residues) and an upstream element (77 residues) which most probably constitutes the N-terminal transit peptide that directs the polypeptide into chloroplasts. In vitro transcription and translation of this construct generates a polypeptide of approximately 21 kDa, which is imported by isolated spinach chloroplasts and processed to the mature 12.5-kDa protein.
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PMID:Primary structure of spinach-chloroplast thioredoxin f. Protein sequencing and analysis of complete cDNA clones for spinach-chloroplast thioredoxin f. 273 3

Thioredoxin, a dithiol polypeptide, has been examined as a potential contributor to the recovery of lens epithelial cells from oxidative insult. It is reported that Escherichia coli thioredoxin can (a) effectively reduce lens-soluble protein disulfide bonds generated by H2O2, (b) restore to its initial activity H2O2-inactivated glyceraldehyde-3-phosphate dehydrogenase, (c) act as an effective source of reducing potential for lens methionine sulfoxide peptide reductase, and (d) act as a free radical quencher based on studies with a stable free radical system generated by ascorbic acid and 2,6-dimethoxy-p-benzoquinone. Thioredoxin is much more effective than dithiothreitol in restoring glyceraldehyde-3-phosphate dehydrogenase activity and as a cofactor for methionine sulfoxide peptide reductase. Upon incubation with epithelial cells, thioredoxin can be observed in the cell using rocket immunoelectrophoresis. These cells recover from H2O2 insult more rapidly than control cell preparations based upon 1) analyses of plasma membrane-related activities: leucine and 86Rb uptake and 2) analyses of parameters primarily related to the internal cell metabolism: ATP concentration and glyceraldehyde-3-phosphate dehydrogenase activity. Analysis of thioredoxin in cell preparations indicates that only about 9% is in the reduced state implying a low effective concentration of the polypeptide. The experiments suggest that low levels of thioredoxin may significantly increase the ability of lens epithelial cells to recover from exposure to H2O2.
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PMID:The effect of H2O2 upon thioredoxin-enriched lens epithelial cells. 283 16


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