Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AN9 is a glutathione S-transferase from petunia (Petunia hybrida) required for efficient anthocyanin export from the site of synthesis in the cytoplasm into permanent storage in the vacuole. For many xenobiotics it is well established that a covalent glutathione (GSH) tag mediates recognition of molecules destined for vacuolar sequestration by a tonoplast-localized ATP-binding cassette pump. Here we inquired whether AN9 catalyzes the formation of GSH conjugates with flavonoid substrates. Using high-performance liquid chromatography analysis of reaction mixtures containing enzyme, GSH, and flavonoids, including anthocyanins, we could detect neither conjugates nor a decrease in the free thiol concentration. These results suggest that no conjugate is formed in vitro. However, AN9 was shown to bind flavonoids using three assays: inhibition of the glutathione S-transferase activity of AN9 toward the common substrate 1-chloro 2,4-dinitrobenzene, equilibrium dialysis, and tryptophan quenching. We conclude that AN9 is a flavonoid-binding protein, and propose that in vivo it serves as a cytoplasmic flavonoid carrier protein.
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PMID:AN9, a petunia glutathione S-transferase required for anthocyanin sequestration, is a flavonoid-binding protein. 1093 72

(R)-3-Hydroxybutyrate dehydrogenase (BDH) is a lipid-requiring mitochondrial enzyme that has a specific requirement of phosphatidylcholine (PC) for function. The C-terminal domain (CTBDH) of human heart BDH (residues 195-297) has now been expressed in Escherichia coli as a chimera with a soluble protein, glutathione S-transferase (GST), yielding GST-CTBDH, a novel fusion protein that has been purified and shown to selectively bind to PC vesicles. Both recombinant human heart BDH (HH-Histag-BDH) and GST-CTBDH (but not GST) form well-defined protein-lipid complexes with either PC or phosphatidylethanolamine (PE)/diphosphatidylglycerol (DPG) vesicles (but not with digalactosyl diglyceride vesicles) as demonstrated by flotation in sucrose gradients. The protein-PC complexes are stable to 0.5 M NaCl, but complexes of either HH-Histag-BDH or GST-CTBDH with PE/DPG vesicles are dissociated by salt treatment. Thrombin cleavage of GST-CTBDH, either before or after reconstitution with PC vesicles, yields CTBDH (12 111 Da by MALDI mass spectrometry) which retains lipid binding without attached GST. The BDH activator, 1-palmitoyl-2-(1-pyrenyl)decanoyl-PC (pyrenyl-PC), at <2.5% of total phospholipid in vesicles, efficiently quenches a fraction (0.36 and 0.47, respectively) of the tryptophan fluorescence of both HH-Histag-BDH and GST-CTBDH with effective Stern-Volmer quenching constants, (K(Q))(eff), of 11 and 9.3 (%)(-)(1), respectively (half-maximal quenching at approximately 0.1% pyrenyl-PC). Maximal quenching by pyrenyl-PC obtains at approximately stoichiometric pyrenyl-PC to protein ratios, reflecting high-affinity interaction of pyrenyl-PC with both HH-Histag-BDH and GST-CTBDH. The analogous pyrenyl-PE effects a similar maximal quenching of tryptophan fluorescence for both proteins but with approximately 15-fold lower (K(Q))(eff) (half-maximal quenching at approximately 1.5% pyrenyl-PE) referable to nonspecific interaction of pyrenyl-PE with HH-Histag-BDH or GST-CTBDH. Thus, the 103-residue CTBDH constitutes a PC-selective lipid binding domain of the PC-requiring BDH.
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PMID:(R)-3-hydroxybutyrate dehydrogenase: selective phosphatidylcholine binding by the C-terminal domain. 1100 6

The conformational stabilities of two homodimeric class mu glutathione transferases (GSTM1-1 and GSTM2-2) were studied by urea- and guanidinium chloride-induced denaturation. Unfolding is reversible and structural changes were followed with far-ultraviolet circular dichroism, tryptophan fluorescence, enzyme activity, chemical cross-linking, and size-exclusion chromatography. Disruption of secondary structure occurs as a monophasic transition and is independent of protein concentration. Changes in tertiary structure occur as two transitions; the first is protein concentration dependent, while the second is weakly dependent (GSTM1-1) or independent (GSTM2-2). The second transition corresponds with the secondary structure transition. Loss in catalytic activity occurs as two transitions for GSTM1-1 and as one transition for GSTM2-2. These transitions are dependent upon protein concentration. The first deactivation transition coincides with the first tertiary structure transition. Dimer dissociation occurs prior to disruption of secondary structure. The data suggest that the equilibrium unfolding/refolding of the class mu glutathione transferases M1-1 and M2-2 proceed via a three-state process: N(2) <--> 2I <--> 2U. Although GSTM1-1 and GSTM2-2 are homologous (78% identity/94% homology), their N(2) tertiary structures are not identical. Dissociation of the GSTM1-1 dimer to structured monomers (I) occurs at lower denaturant concentrations than for GSTM2-2. The monomeric intermediate for GSTM1-1 is, however, more stable than the intermediate for GSTM2-2. The intermediates are catalytically inactive and display nativelike secondary structure. Guanidinium chloride-induced denaturation yields monomeric intermediates, which have a more loosely packed tertiary structure displaying enhanced solvent exposure of its tryptophans and enhanced ANS binding. The three-state model for the class mu enzymes is in contrast to the equilibrium two-state models previously proposed for representatives of classes alpha/pi/Sj26 GSTs. Class mu subunits appear to be intrinsically more stable than those of the other GST classes.
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PMID:Equilibrium folding of dimeric class mu glutathione transferases involves a stable monomeric intermediate. 1101 13

LINE-1, or L1, is a non-LTR retrotransposon in mammals. Retrotransposition of L1 requires the action of two element-encoded proteins, ORF1p and ORF2p. ORF2p provides essential enzymatic activities for the reverse transcription and integration of a newly transposed copy of L1, whereas the exact role of ORF1p is less well understood. The 43 kDa ORF1p copurifies as a large complex with L1 RNA in extracts of human and mouse cells. Mouse ORF1p purified from Escherichia coli binds RNA and single-stranded DNA in vitro, exhibits nucleic acid chaperone activity, and is capable of protein-protein interaction. In this study we create a series of deletions in the ORF1 sequence, express the truncated proteins and examine their activities to delineate the region of ORF1p responsible for these different functions. By both yeast two-hybrid analysis and GST pull-down assay, the protein-protein interaction domain is defined as a coiled-coil domain that encompasses about one third of the protein near its N terminus. Based on data obtained with UV-cross-linking, electrophoretic mobility-shift assay and an annealing assay, the C-terminal one third of ORF1p is both necessary and sufficient for nucleic acid binding and to promote annealing of complementary oligonucleotides. Separation of these activities into different domains of ORF1p will facilitate detailed biochemical analyses of the structure and function of this protein and understanding of its role during L1 retrotransposition.
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PMID:Deletion analysis defines distinct functional domains for protein-protein and nucleic acid interactions in the ORF1 protein of mouse LINE-1. 1107 6

Dictyostelium myosin II heavy chain kinase A (MHCK A), MHCK B, and MHCK C contain a novel type of protein kinase catalytic domain that displays no sequence identity to the catalytic domain present in conventional serine, threonine, and/or tyrosine protein kinases. Several proteins, including myelin basic protein, myosin regulatory light chain, caldesmon, and casein were phosphorylated by the bacterially expressed MHCK A, MHCK B, and MHCK C catalytic domains. Phosphoamino acid analyses of the proteins showed that 91 to 99% of the phosphate was incorporated into threonine with the remainder into serine. Acceptor amino acid specificity was further examined using a synthetic peptide library (MAXXXX(S/T)XXXXAKKK; where X is any amino acid except cysteine, tryptophan, serine, and threonine and position 7 contains serine and threonine in a 1.7:1 ratio). Phosphorylation of the peptide library with the three MHCK catalytic domains resulted in 97 to 99% of the phosphate being incorporated into threonine, while phosphorylation with a conventional serine/threonine protein kinase, the p21-activated kinase, resulted in 80% of the phosphate being incorporated into serine. The acceptor amino acid specificity of MHCK A was tested directly by substituting serine for threonine in a synthetic peptide and a glutathione S-transferase fusion peptide substrate. The serine-containing substrates were phosphorylated at a 25-fold lower rate than the threonine-containing substrates. The results indicate that the MHCKs are specific for the phosphorylation of threonine.
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PMID:Specific phosphorylation of threonine by the Dictyostelium myosin II heavy chain kinase family. 1127 93

The mammalian gene products, transient receptor potential (trp)1 to trp7, are related to the Drosophila TRP and TRP-like ion channels, and are candidate proteins underlying agonist-activated Ca(2+)-permeable ion channels. Recently, the TRP4 protein has been shown to be part of native store-operated Ca(2+)-permeable channels. These channels, most likely, are composed of other proteins in addition to TRP4. In the present paper we report the direct interaction of TRP4 and calmodulin (CaM) by: (1) retention of in vitro translated TRP4 and of TRP4 protein solubilized from bovine adrenal cortex by CaM-Sepharose in the presence of Ca(2+), and (2) TRP4-glutathione S-transferase pull-down experiments. Two domains of TRP4, amino acid residues 688-759 and 786-848, were identified as being able to interact with CaM. The binding of CaM to both domains occurred only in the presence of Ca(2+) concentrations above 10 microM, with half maximal binding occurring at 16.6 microM (domain 1) and 27.9 microM Ca(2+) (domain 2). Synthetic peptides, encompassing the two putative CaM binding sites within these domains and covering amino acid residues 694-728 and 829-853, interacted directly with dansyl-CaM with apparent K(d) values of 94-189 nM. These results indicate that TRP4/Ca(2+)-CaM are parts of a signalling complex involved in agonist-induced Ca(2+) entry.
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PMID:The transient receptor potential, TRP4, cation channel is a novel member of the family of calmodulin binding proteins. 1131 Nov 28

Kinetic evidence suggests an acidic region in nardilysin binds polyamines and acts as a regulatory domain. The binding of approximately 5 mol of spermine/mol of nardilysin was demonstrated. The binding curve was sigmoidal exhibiting an IC(50) of approximately 118 microM and a Hill coefficient of 1.8. Spermine diminished the tryptophan fluorescence of the enzyme and increased its sensitivity to protease V8. The acidic stretch from mouse and human nardilysin were expressed as glutathione transferase fusion proteins. All fusion proteins bound spermine with an IC(50) of 40 to 110 microM. The mouse fusion protein bound approximately 7 mol of spermine exhibiting a sigmoidal binding curve and a Hill coefficient of 1.4. The human acidic stretch, containing fewer acidic residues, bound approximately 5 mol of spermine/mol with a hyperbolic binding curve. Chimeric fusion proteins containing the N-terminus of the mouse acidic region fused to the C-terminus of the human acidic region bound approximately 10 mol of spermine, while the opposite chimera bound approximately 4 mol of spermine/mol. The N-terminal region of the mouse acidic domain binds 3--4 mol spermine/mol exhibiting a Hill coefficient of 1.4, while the same region from human nardilysin binds 1 mol of spermine/mol. Spermine enhanced the sensitivity of the mouse acidic domain, but not the human acidic domain, to protease V8. Together the data support a model where the acidic stretch of nardilysin functions as an autonomous domain.
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PMID:Expression of the acidic stretch of nardilysin as a functional binding domain. 1147 15

Oxysterol-binding protein (OSBP) is 1 of 12 related proteins implicated in the regulation of vesicle transport and sterol homeostasis. A yeast two-hybrid screen using full-length OSBP as bait was undertaken to identify partner proteins that would provide clues to the function of OSBP. This resulted in the cloning of vesicle-associated membrane protein-associated protein-A (VAP-A), a syntaxin-like protein implicated in endoplasmic reticulum (ER)/Golgi vesicle transport, and phospholipid regulation in mammalian cells and yeast, respectively. By using a combination of yeast two-hybrid, glutathione S-transferase pull-down and immunoprecipitation experiments, the VAP-A-binding region in OSBP was localized to amino acids 351-442. This region did not include the pleckstrin homology (PH) domain but overlapped with the N terminus of the oxysterol binding and OSBP homology domains. C- and N-terminal truncations or deletions of VAP prevented interaction with OSBP but did not affect VAP multimerization. Although the OSBP PH domain was not necessary for VAP-A binding in vitro, interaction with VAP-A was enhanced in cells by mutation of the conserved PH domain tryptophan (OSBP W174A) or deletion of the C-terminal half of the PH domain (OSBP Delta 132-182). OSBP W174A retained oxysterol binding activity, association with phospholipid vesicles via the PH domain, and localized with VAP in unusual ER-associated structures. At 40 degrees C, misfolded ts045-vesicular stomatitis virus G protein fused to green fluorescent protein was co-localized with VAP-A/OSBP W174A structures on the ER but was exported to the Golgi when folded normally at 32 degrees C. A fluorescent ceramide analogue also accumulated in these ER inclusions, and export to the Golgi was partially inhibited as indicated by decreased Golgi staining and a 30% reduction in sphingomyelin synthesis. These studies show that OSBP binding to the ER and Golgi apparatus is regulated by its PH domain and VAP interactions, and the complex is involved at a stage of protein and ceramide transport from the ER.
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PMID:Vesicle-associated membrane protein-associated protein-A (VAP-A) interacts with the oxysterol-binding protein to modify export from the endoplasmic reticulum. 1202 75

The fragments of the androgen receptor (amino acids: 359-732) and of the glucocorticoid receptor (amino acids: 396-548) were expressed in E. coli as fusion proteins with GST. Both fusion proteins, denoted GST-AR and GST-GR, contained the DNA-binding domain and some flanking amino acids. In gel retardation assay both fusion proteins could bind the androgen/glucocorticoid response element (ARE/GRE). We found that both cytosol and nuclear extracts from rat ventral prostate (v.p), but not from other source tested could abolish the interaction of GST-AR and GST-GR with ARE/GRE (from C3 (1) gene and MMTV LTR). The inhibition was androgen-dependent and sensitive to temperature and trypsin treatment. It implies that a protein inhibitor was present in the rat ventral prostate.
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PMID:A prostate-specific Protein Factor Inhibits the Interaction of Androgen Receptors with Hormone Response Elements. 1216 99

Signal transduction pathways induced by cytokines can modulate the level of HIV-1 gene transcription and replication in a variety of cells including those from the central nervous system. Here, we investigated the effect of TGFbeta-1 signaling the factors, including Smads, on transcription of the viral LTR in human astrocytic cells. Ectopic expression of Smad-3 increased activity of the viral promoter, while its partner protein, Smad-4, caused a slight decrease in viral gene transcription. Further, Smad-4 was able to suppress transcriptional activation of the LTR by Smad-3 as well as by C/EBPbeta, another activator of LTR transcription in these cells. Results from promoter deletion experiments identified the C/EBP-binding site, which is positioned between nucleotides -114 and -102 as one of the targets for Smad-mediated regulation of the LTR. Band-shift studies showed inhibition of C/EBP binding to its target DNA in protein extract from cells overexpressing Smad-3 and Smad-4. Results from GST pull-down assay and combined immunoprecipitation/Western blot of protein extracts from human astrocytes verified the association of Smad-3 and Smad-4 with C/EBPbeta, suggesting that interaction of C/EBPbeta with Smad-3 and Smad-4 may have a negative impact upon C/EBPbeta-mediated activation of the LTR. Interestingly, Smad-4 showed no inhibitory effect on viral gene transcription in cells expressing Tat protein. However, in the presence of Smad-3, expression of Smad-4 exerted a negative effect on Tat-mediated activation of the LTR promoter. These observations pointed to the functional interplay between viral and cellular proteins in modulating LTR transcription.
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PMID:Interaction between TGFbeta signaling proteins and C/EBP controls basal and Tat-mediated transcription of HIV-1 LTR in astrocytes. 1220 26


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