Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ilvIH operon of Escherichia coli encodes acetohydroxyacid synthase III, an isoenzyme involved in branched-chain amino acid biosynthesis. Transcription of the ilvIH operon is repressed by growing cells in the presence of leucine (C.H. Squires, M. DeFelice, S.R. Wessler, and J.M. Calvo, J. Bacteriol. 147:797-804, 1981). A protein in crude extracts of E. coli, termed the ilvIH-binding (IHB) protein, bound specifically in vitro to DNA upstream of the ilvIH operon. The binding protein, partially purified by Polymin precipitation, gel filtration, and phosphocellulose chromatography, has a native molecular weight of 43,000 and is composed of two subunits of identical size. As determined by protection against lambda exonuclease and DNase I, the protein binds within a region -190 to -260 relative to the start point of transcription. In addition, the IHB protein binds to a site between positions -100 and -40. The following evidence suggests that binding of this protein to the region upstream of ilvIH is related to the regulation of this operon by leucine. Binding of the IHB protein to the ilvIH regulatory region in vitro was reduced by leucine but not by isoleucine, valine, or threonine. In a mutant strain isolated by M.V. Ursini, P. Arcari, and M. DeFelice (Mol. Gen. Genet. 181:491-496, 1981), transcription was not repressed by leucine. A protein in extracts of this mutant strain bound to the ilvIH regulatory region, but the complex migrated through agarose gels with a mobility different from that of the complex formed by wild-type protein. Furthermore, a concentration of leucine that substantially reduced binding of the wild-type to DNA did not affect binding of the protein from the mutant strain. A simple model consistent with these findings is that transcription from the ilvIH promoter is stimulated by binding the IHB protein to one or more sites upstream of the promoter and that leucine interferes with this binding.
 ...
PMID:A protein that binds to the regulatory region of the Escherichia coli ilvIH operon. 264 91

The filter-binding technique with PEI treated glass fiber is used to study the interaction of histone H5 to core particles, chromatosomes and DNA derived from it. By working at very low concentrations of interacting particles we are able to study the effective binding process independent of interfering insoluble complexes. The interactions are characterized by a very high affinity. An intrinsically higher affinity of H5 for cores and chromatosomes versus chromatosome derived DNA is demonstrated. Both chromatosomes and DNA derived from these bind about twice the amount as compared to core particles, which saturate at about one H5 per core particle.
Mol Biol Rep
PMID:Comparative filter binding study of H5 to nucleosome core particles, H1, H5 depleted chromatosomes and DNA fragments. 327 46

Porfiromycin was reductively metabolized by NADPH cytochrome P-450 reductase and xanthine oxidase under anaerobic conditions. The production of metabolites varied with the pH and the contents of the reaction buffer. In Tris buffer, two major metabolites were produced at pH 7.5 and above, whereas one major metabolite was produced at pH 6.5. The three major metabolites were separated and isolated by HPLC. Identification by californium-252 plasma desorption mass spectrometry showed that the two major metabolites from pH 7.5 were (trans) and (cis)-forms of 7-amino-1-hydroxyl-2-methylaminomitosene and the major metabolite from pH 6.5 was 7-amino-2-methylaminomitosene. All three major metabolites showed substitutions at the C-1 position. DNA was alkylated readily by enzyme-activated porfiromycin. Digestion of porfiromycin-alkylated DNA by DNase, snake venom phosphodiesterase, and alkaline phosphatase resulted in an insoluble nuclease-resistant fraction and a soluble fraction. The nuclease-resistant fraction reflected a high content of cross-linked adducts. Upon HPLC analysis, the solubilized fraction contained two monofunctionally linked porfiromycin adducts and a possibly cross-linked dinucleotide. The major adduct was isolated by HPLC and identified by NMR, as N2-(2'-deoxyguanosyl)-7-amino-2-methylaminomitosene. The N2 position of deoxyguanosine appeared as the major monofunctional alkylating site for DNA alkylation by porfiromycin. Thus, mitomycin C and porfiromycin (which differs from mitomycin C only by the addition of a methyl group to the aziridine nitrogen) share the same enzymatic activating mechanism that leads to the formation of the same types of metabolites and the same specificity of DNA alkylation.
Mol Pharmacol 1988 Aug
PMID:Metabolites and DNA adduct formation from flavoenzyme-activated porfiromycin. 341 25

Electron microscopic cytochemical studies on human ventricular muscles obtained during open heart surgery were carried out in ten patients with tetralogy of Fallot. Polyethyleneimine was used as a tracer for demonstration of anionic sites in the membrane surfaces of myocardial cells and capillaries. In the myocardial cells PEI particles were consistently observed to be orderly arranged in the external lamina of normal basement membranes at regular spacings of 40 to 80 nm. Few PEI particles were irregularly dispersed in the surface coat of basement membranes and the interspaces of intercalated discs. PEI particles were also seen to be regularly distributed in normal capillary basement membranes, mainly restricted in outer lamina densa at intervals of 40 to 80 nm. It was of particular interest that PEI particles were often seen to be irregularly and loosely arranged in abnormally thickened basement membranes of myocardial cells and capillaries. In addition, focal loss of PEI deposition in altered basement membranes was a frequent finding. Based on electron microscopic cytochemical findings the following conclusions are made: The anionic sites characterized by PEI which is considered to be superior to most polycationic colloids show a regular lattice-like arrangement in the basement membranes of human myocardial cells and capillaries; Anionic groups which are not distributed uniformly on human myocardial cell surfaces show different distribution patterns in the external lamina and surface coat of basement membranes; and Perturbations of regular anionic arrays are demonstrable in altered basement membranes of diseased human myocardium.
J Mol Cell Cardiol 1986 May
PMID:Appraisal of polyethyleneimine used as a tracer for anionic sites in human cardiac tissues with a brief reference to anionic molecular organization in altered basement membranes. 372 99

Cytosoluble estradiol-receptor (ER) complexes obtained from uteri of castrated rats show a 4.3 S sedimentation coefficient when analysed by sucrose gradient in high salt buffer both in the absence and presence of 0.1 M ammonium thiocyanate. After incubation with nuclei, the complexes sediment at 4.3 S and at 3.2 S, in the absence and presence of 0.1 M ammonium thiocyanate respectively. This structural modification of ER is also confirmed by gel filtration analysis. In similar conditions hydroxytamoxifen-ER complexes apparently do not undergo such a modification. However, increasing the molarity of the chaotropic ion up to 0.5 M shows that, in fact, the modification occurs. Sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis of covalently linked tamoxifen aziridine-ER 'complexes' confirms that the nuclear treatment reduces the apparent molecular weight of ER from 62 000 to 47 000. These data demonstrate that, in vitro, nuclear ER is cleaved into a smaller molecular form and that the receptor fragments can be held together by the triphenylethylene antiestrogen hydroxytamoxifen.
Mol Cell Endocrinol 1986 Sep
PMID:Different interaction of estradiol and antiestrogens with the estrogen receptor of rat uterus. 374 88

The one-electron electrochemical reduction of diaziquone was analyzed using electron spin resonance and compared to its enzymatic reduction. Two analogues were used to help the analysis. The analogues contained chlorine atoms which substituted either the carboethoxyamino groups or the aziridine groups of the parent compound. The diaziquone free radical produced electrochemically in dimethyl sulfoxide exhibited an 11-line electron spin resonance spectrum. The hyperfine couplings responsible for this spectrum were due to the aziridine nitrogens (aNAz), and the imide hydrogens (aHNHR) and nitrogens (aNNHR) of the carboethoxyamino groups. The couplings had the following order of strength: (aNAz) greater than (aHNHR) greater than (aNNHR). The nuclei responsible for the (aNAz) and (aHNHR) coupling were found to be magnetically inequivalent. Adding water to the dimethyl sulfoxide solution of electrochemically reduced diaziquone changed its 11-line ESR spectrum to a 5-line spectrum identical to the one observed for enzymatically reduced diaziquone. Hence, the identity of this latter free radical was resolved. Electrochemically reduced free radicals of antitumor agents can be used to understand biologically reduced ones and thus explore drug activity-free radical structure relationships.
Mol Pharmacol 1984 Nov
PMID:Free radicals in quinone-containing antitumor agents. Electrochemical reduction of diaziquone (2,5-diaziridine-3,6-bis(carboethoxyamino)-1,4 -benzoquinone) and two analogues. 609 3

The antilactogen binding site (ALBS) is a membrane associated protein to which tamoxifen (TAM) and related non-steroidal antiestrogens, but not estrogen, bind. It is through this site that TAM inhibits lactogen binding to the prolactin (Prl) receptor and subsequent Prl induced growth and differentiation in target tissues. Binding of lactogens to the Prl receptor is inhibited by TAM or 4-hydroxy-TAM at 4 degrees C as well as room temperature, thus suggesting that the ALBS is not an enzyme. TAM acts by inhibiting the binding of lactogens to the receptor rather than promoting dissociation of the hormone-receptor complex. Lactogens bind to mammary gland membranes with an Kd of 4.3-8.2 x 10(-10) M. In the presence of 10(-7) M TAM the affinity decreased to a Kd of 0.8-1.6 x 10(-9) M. Binding of 3H-TAM to mammary gland membranes was effectively inhibited by an anti-Prl receptor antibody, thus suggesting a close relationship between the Prl receptor and the ALBS. Separate affinity purification of the ALBS and the Prl receptor resulted in peak fractions demonstrating specific binding activity for both TAM and lactogenic hormones. Re-isolation of the affinity purified Prl receptor on a TAM-Sepharose affinity resin again resulted in co-elution of both binding activities. The isolates from both affinity resins contained primarily a single band with an apparent molecular mass of 90 kDa. This band was precipitated with the anti-Prl receptor antibody and specifically bound the affinity label ring-3H-TAM aziridine.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1993 Dec
PMID:Characteristics of a membrane-associated antilactogen binding site for tamoxifen. 814 9

Oestrogen receptors (ERs) in breast tumours are highly heterogeneous. In previous studies we have shown that at least four isoforms may exist. These migrate in isoelectric focusing (IEF) gels to isoelectric points (pI values) 6.1, 6.3, 6.6 and 6.8. Of these the first (pI 6.1) corresponds to the 8S isoform as detected by sucrose gradient fractionation, while the others all sediment at 4S. In a series of 66 breast tumours it was found that those at pI 6.3 and pI 6.8 were significantly correlated with the presence of progesterone receptors. To characterize the isoforms more fully, ER isoforms labelled by [3H]oestradiol binding were fractionated by IEF. The results were compared with those obtained after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using the H222 anti-ER monoclonal antibody. In other experiments, tumour ER isoforms were covalently labelled with [ring-3H] tamoxifen aziridine and separated by IEF. The individual isoforms were electroeluted from the IEF gel and further analysed by SDS-PAGE and non-denaturing PAGE. In summary, the evidence shows that the isoforms of pI values 6.3, 6.8 and 6.6 have molecular masses of 50, 65 and 70 kDa respectively. In addition, all three of these isoforms, i.e. the pI 6.3, 6.8 and 6.6 isoforms, could form dimers. We conclude that the three isoforms sedimenting at 4S have the capacity to form dimers and thus may have the potential for binding to oestrogen response elements in the genome.
J Mol Endocrinol 1993 Aug
PMID:The nature and significance of multiple isoforms of the oestrogen receptor in breast tumours. 824 Jun 75

The estrogen receptor (ER) is a rapidly turning over protein, with a half-life of ca. 3-4 h in estrogen target cells. Sequence analysis of the human ER reveals a putative PEST sequence, sequences rich in proline (P), glutamic acid (E), serine (S) and threonine (T), in the carboxy-terminal F domain of the protein. Since PEST sequences have been implicated in the rapid turnover of some proteins, we have used site-directed mutagenesis to investigate the role of the F region containing PEST residues in the stability and bioactivity of the receptor. A truncated form of ER lacking the last 41 amino acids of the protein and encompassing the PEST sequences (amino acids 555 to 567) was made by mutagenesis of the ER cDNA. Pulse-chase experiments, involving immunoprecipitation of [35S]methionine/[35S]cysteine labeled receptors or of receptors covalently labeled with tamoxifen aziridine followed by gel electrophoresis, were used to determine the half-life of the wild-type and truncated ERs. These experiments showed that the turnover rate of the receptors expressed in Chinese hamster ovary and monkey kidney (COS-1) cells was 3 to 5 h and that elimination of the PEST residues did not have a significant effect on the degradation rate of the protein. Moreover, deletion of the last 41 amino acids (F domain) of the ER did not affect transactivation ability, ligand binding affinity, or the phosphorylation pattern of the receptor. Therefore, the role of domain F in ER function remains unclear, but it is not a determinant of the relatively rapid rate of ER turnover in cells.
J Steroid Biochem Mol Biol 1993 Dec
PMID:An assessment of the role of domain F and PEST sequences in estrogen receptor half-life and bioactivity. 827

We have used affinity labeling, site-directed mutagenesis and regional chemical mutagenesis in order to determine regions of the human estrogen receptor (ER) important in hormone binding, ligand discrimination between estrogens and antiestrogens, and transcriptional activation. Affinity labeling studies with the antiestrogen, tamoxifen aziridine and the estrogen, ketononestrol aziridine have identified cysteine 530 in the ER hormone binding domain as the primary site of labeling. In the absence of a cysteine at 530 (i.e. C530 mutant), C381 becomes the site of estrogen-compatible tamoxifen aziridine labeling. Hence these two residues, although far apart in the primary linear sequence of the ER protein, must be close in the three-dimensional structure of the protein, in the ER ligand binding pocket, so that the ligand can reach either site. Site-directed mutagenesis of selected residues in the ER and region-specific chemical mutagenesis of the ER hormone binding domain with initial phenotypic screening in yeast have enabled the identification of a region near C530 important in discrimination between estrogens and antiestrogens and of other residues important in hormone-dependent transcriptional activation. Some ER mutants with alterations in the carboxy-terminal portion of the hormone binding domain are transcriptionally inactive yet bind hormone and also function as potent dominant negative ERs, suppressing the activity of wild-type ER at low concentrations. These studies reveal a separation of the hormone binding and transcription activation functions of the ER. They are also beginning to provide a more detailed picture of the ER hormone binding domain and amino acids important in ligand binding and discrimination between different categories of agonist and antagonist ligands. Such information will be important in the design of maximally effective antiestrogens. In addition, since there is now substantial evidence for a mixture of wild-type and variant ERs in breast cancers, our studies should provide insight about the bioactivities of these variant receptors and their roles in modulating the activity of wild type ER, and should lead to a better understanding of the possible role of variant receptors in altered response or resistance to antiestrogen and endocrine therapy in breast cancer. In addition, some dominant negative receptors may prove useful in examining ER mechanisms of action and in suppressing the estrogen-dependent growth of breast cancer cells.
J Steroid Biochem Mol Biol 1993 Dec
PMID:Hormone binding and transcription activation by estrogen receptors: analyses using mammalian and yeast systems. 827 40


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>