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

Iron is an essential nutrient for Trichomonas vaginalis and is acquired via highly specific receptor-mediated mechanisms from the host. Responses of T. vaginalis to conditions of iron limitation or iron excess were analysed in order to determine whether iron levels in the growth medium regulate certain properties of the parasite. When compared with organisms grown in excess iron, iron limitation resulted in greater than or equal to 80% lower rates of protein synthesis and greater than or equal to 3-fold decreases in cell densities. These parasites also exhibited generation times of approximately 10 hours, 2.5-fold longer than organisms grown in the usual complex medium. Iron-restricted growth also resulted in increased binding of lactoferrin by trichomonads, which paralleled elevated expression of the lactoferrin-binding receptor protein having a relative molecular mass of 136,000 daltons (136 kDa). A Mr 126 kDa protein was concomitantly repressed in low-iron-grown parasites. The greater amounts of lactoferrin bound by iron-depleted T. vaginalis organisms corresponded with both the expression of additional receptors onto trichomonal surfaces and increased affinity of the receptor for the lactoferrin molecule. Finally, immunoblot analysis of parasites grown under high- and low-iron conditions using sera from patients with trichomoniasis further revealed the synthesis by T. vaginalis of at least 19 iron-regulated immunogens, and patients' sera also detected the lactoferrin receptor. These data not only show the overall importance of iron to the biology of this protozoan, but illustrate the in vivo iron modulation of gene expression of the biofunctional lactoferrin receptor and other immunogens.
Mol Microbiol 1992 Jan
PMID:Iron regulates growth of Trichomonas vaginalis and the expression of immunogenic trichomonad proteins. 131 Jul 92

The amino terminal half of human lactoferrin (LfN) produced from transfected baby hamster kidney cells has been crystallized in its iron-saturated and iron-free forms. The crystals of glycosylated LfN and deglycosylated LfN are monoclinic, space group C2, with cell dimensions a = 133.0 A, b = 58.3 A, c = 58.3 A, alpha = 90.0 degrees, beta = 114.7 degrees, gamma = 90.0 degrees, and one molecule per asymmetric unit. Crystals of apo LfN have also been prepared using deglycosylated protein. These crystals are tetragonal, space group P4(1)2(1)2 (or P4(3)2(1)2), with cell dimensions of a = b = 58.4 A and c = 217.2 A and one molecule per asymmetric unit. Both the iron-saturated and the iron-free crystals are suitable for high resolution X-ray analysis.
J Mol Biol 1992 Dec 05
PMID:Preliminary crystallographic studies of the amino terminal half of human lactoferrin in its iron-saturated and iron-free forms. 146 29

The 5'-flanking region of the human lactoferrin gene was isolated from a human placental genomic library. This genomic clone contains a 16-kilobase pair (kbp) insert and produces seven fragments when digested with the SacI restriction enzyme. We sequenced one of the fragments that comprises 1294 bp of the 5'-flanking sequence, 79 bp of the first exon, and 690 bp of the first intron. A major transcription start site was mapped by primer extension. The region immediately upstream from the transcription initiation site following the first exon is abundant in G and C nucleotides. In the promoter and 5'-flanking region within a 300-bp stretch (-465 to -165) of the DNA, we found a noncanonical TATA box (ATAAA), CAAT-like sequence (CAAC) and sequences homologous to the consensus SP1 binding site, Pu.1/Sp.1 binding element (PU box), two half-palindromic estrogen response elements (EREs; GGTCA), an imperfect ERE (GGTCAAGGCGATC), and a sequence resembling the chicken ovalbumin upstream promoter transcription factor (COUP-TF) binding site (GTCTCACAGGTCA). The COUP-TF binding site and the imperfect ERE shared five nucleotides (GGTCA). With the exception of the two half-palindromic EREs, the elements with very well matched sequences were also found in the corresponding positions in the mouse lactoferrin gene. The synthetic oligonucleotide, including the 26 bp of COUP/ERE sequence, was cloned before the SV40 promoter in a chloramphenicol acetyltransferase reporter construct. These chimeric plasmids were transiently transfected into human endometrium carcinoma RL95-2 cells to assess hormone responsiveness. We found that the COUP/ERE element acted as an enhancer in response to estrogen stimulation. In vitro DNase I footprinting analysis showed binding of the estrogen receptor on the imperfect ERE. In contrast to the mouse lactoferrin COUP/ERE element, COUP-TF does not interact with this element, as demonstrated by band shift assay and site-directed mutagenesis. Therefore, the molecular mechanisms of the estrogen action that govern the lactoferrin gene expression differ between mouse and human.
Mol Endocrinol 1992 Nov
PMID:Differential molecular mechanism of the estrogen action that regulates lactoferrin gene in human and mouse. 148 Jan 83

Plasma lactoferrin content was measured before and after therapy with recombinant granulocyte-macrophage colony-stimulating factor in five patients with aplastic anaemia, six with myelodysplasia, and three with prolonged, severe, chemotherapy-induced neutropenia. Before therapy plasma lactoferrin content was uniformly low. However, patients with aplastic anemia and those with chemotherapy-induced neutropenia had a normal lactoferrin:neutrophil ratio. The low levels of plasma lactoferrin thus reflected the low granulocyte mass. On the other hand, patients with myelodysplasia also had reduced lactoferrin:neutrophil ratios, suggesting qualitative/quantitative abnormalities of neutrophil lactoferrin production. After treatment with granulocyte-macrophage colony-stimulating factor, plasma lactoferrin levels increased in patients with aplastic anemia and in those with chemotherapy-induced neutropenia who showed a neutrophil response to treatment. In these patients, the lactoferrin:neutrophil ratio became elevated, suggesting increased synthesis/release of lactoferrin from neutrophils. However, patients with myelodysplasia continued to show depressed lactoferrin:neutrophil ratios, even when there had been an increase in granulocyte count, suggesting persistent abnormalities of neutrophil lactoferrin production/release. The implications of these findings for treatment of neutropenic patients with granulocyte-macrophage colony-stimulating factors are discussed.
Mol Biother 1992 Jun
PMID:Plasma lactoferrin content in neutropenic patients: effects of treatment with recombinant granulocyte-macrophage colony-stimulating factor. 151 94

Previously, we have studied thyroid hormone-dependent growth of GH1 rat pituitary tumor cells in iron-restricted serum-free defined medium (Sirbasku, D.A., et al. (1991) Biochemistry 30, 295-304, 7466-7477). Proliferation was promoted by triiodothyronine (T3) and any of seven forms of horse serum-derived apotransferrin (apoTf). In this report, we have asked if apoTfs from other species also acted as thyromedins and if other metal ion chelators served this role. To address these issues, three thyromedins were isolated from human serum and identified as apoTf. Fe3+ depletion, and assay in low-Fe medium, gave ED50s of 1.4-1.7 nM. Fe3+ saturation abolished their activities in high-Fe medium. To ask if apoTf was the major thyromedin in human serum, hormone-depleted preparations were iron saturated and shown to no longer support T3-dependent GH1 cell growth. Next, commercially prepared human, rat, horse, dog, rabbit, guinea pig and mouse apoTfs were shown to be as active under iron-restricted conditions as those isolated from human serum. Bovine apoTf and colostrum lactoferrin were greater than 100-fold less active; human milk apo-lactoferrin and apo-ovotransferrins were inactive. Transferrins which displayed thyromedin activity blocked the binding of 125I-rat 2Fe.Tf to GH1 cell receptors while those without thyromedin activity were ineffective. Finally, the metal ion chelators EDTA, citrate and deferoxamine did not show thyromedin activity indicating that apoTfs uniquely were able to promote T3-dependent cell growth in defined culture.
Mol Cell Endocrinol 1992 Feb
PMID:Apotransferrins from several species promote thyroid hormone-dependent rat pituitary tumor cell growth in iron-restricted serum-free defined culture. 154 14

Transcription of the lactoferrin gene is stimulated by estrogen in mouse uterus. To study direct estrogen regulation of this gene at the molecular level, we cloned and analyzed the 5'-flanking region of the mouse lactoferrin gene. Sequence analysis revealed a putative estrogen-responsive element (ERE) overlapping with a chicken ovalbumin up-stream promoter (COUP) element located at position -349 to -329 from the transcription initiation site. The ERE element differed from the consensus ERE sequence by one nucleotide at the second position of the 3' half of the element (G to A); the COUP element differed by one nucleotide from the chicken COUP element. Synthetic oligonucleotide containing the mouse lactoferrin COUP/ERE element was inserted into the reporter chloramphenicol acetyltransferase vector, then transiently transfected into human endometrium carcinoma RL95-2 cells to assess hormone responsiveness. We found that the COUP/ERE element confers estrogen action to both homologous and heterologous promoters. Nuclear proteins from diethylstilbestrol-treated mouse uteri and proteins from estrogen receptor expression vector-transfected RL95-2 whole cell extract bound in vitro to COUP/ERE element specifically, as assessed by band-shift assay. By using antibodies specific to the estrogen receptor and the COUP transcription factor, we demonstrated that both proteins were present in mouse uterine tissue and interacted specifically with the COUP/ERE element, as shown by the superband shift. Competition experiments with specific ERE or COUP oligonucleotides also confirmed the interaction between lactoferrin COUP/ERE element with the estrogen receptor and the COUP transcription factor. Therefore, we named this sequence mERM, the mouse lactoferrin estrogen response module.
Mol Endocrinol 1992 Mar
PMID:Estrogen response module of the mouse lactoferrin gene contains overlapping chicken ovalbumin upstream promoter transcription factor and estrogen receptor-binding elements. 158 12

X-ray solution scattering has been used for studying the structural changes that take place upon uptake and release of iron from serum and chicken ovo-transferrin and human lactoferrin. In the case of chicken ovo-transferrin, data have been obtained for both the intact protein and the isolated N and C-lobes with and without iron. These studies reveal that both lobes undergo a change that is consistent with an opening of the inter-domain cleft when iron is removed from the protein. We suggest that the conformational change of the protein increases the specificity of receptor binding and that the closed configuration of the iron-loaded protein is one, or perhaps the, decisive step in the mechanism for receptor-mediated endocytosis.
J Mol Biol 1992 Jun 05
PMID:X-ray solution scattering reveals conformational changes upon iron uptake in lactoferrin, serum and ovo-transferrins. 160 83

Subcellular fractionation studies in resting human neutrophils indicated a bimodal distribution for cytochrome b. A major peak of cytochrome b co-sedimented with gelatinase under different experimental conditions. This localization was partially overlapped with specific granules (using lysozyme and lactoferrin as specific granule markers), but clearly resolved from azurophilic granules, plasma membrane, mitochondria, as well as from a novel alkaline phosphatase-rich intracellular organelle. A minor localization of cytochrome b was found in fractions enriched in both the plasma membrane marker 5'-nucleotidase and alkaline phosphatase. A significant portion of ubiquinone cell content co-fractionated with the gelatinase-containing granules. After phorbol myristate acetate (PMA)-cell stimulation, cytochrome b was mobilized to fractions showing respiratory burst activity and enriched in 5'-nucleotidase activity. This mobilization paralleled secretion of gelatinase and lysozyme to the extracellular medium. Furthermore, neutrophil stimulation with fluoride in the absence of cytochalasin B induced release of gelatinase and generation of superoxide anion with only minimal release of lysozyme. Preincubation of cells with the anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) prevented lysozyme release, but had only a minor effect on the release of gelatinase and did not inhibit the superoxide anion generation elicited by N-formyl-methionyl-leucyl-phenylalanine or PMA. These results suggest a main location of cytochrome b in mobilizable gelatinase-containing granules, which can constitute a subpopulation of specific granules. Furthermore, these findings show that the gelatinase-containing granule is functionally involved in the respiratory burst in neutrophils and that membrane fusion between plasma membrane and the gelatinase-containing granule occurs during activation of cells.
Mol Cell Biochem 1991 Jun 26
PMID:Cytochrome b co-fractionates with gelatinase-containing granules in human neutrophils. 165 2

A comparison of Cu K-edge x.a.f.s. spectra with that of the equivalent Fe K-edge for chicken ovotransferrin (COT) indicates that the metal ions occupy essentially the same binding sites in the protein. However, in the case of the Cu2+ complex the metal appears to have reduced co-ordination. Changes are observed in the x.a.f.s. of 90%-saturated COT (Cu1.8COT) on freeze-drying. The three-dimensional X-ray structures of rabbit serum transferrin and human lactoferrin have shown that the ferric cations are co-ordinated by four protein ligands and a bidentate carbonate anion in a distorted octahedral arrangement [Anderson, Baker, Dodson, Norris, Rumball, Waters & Baker (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 1768-1774; Anderson, Baker, Norris, Rice and Baker (1989) J. Mol. Biol. 209, 711-734; Bailey, Evans, Garratt, Gorinsky, Hasnain, Horsburgh, Jhoti, Lindley, Mydin, Sarra & Watson (1988) Biochemistry 27, 5804-5812]. This structural information, together with the differences in e.x.a.f.s. spectra for solution and freeze-dried samples of diferric COT [Hasnain, Evans, Garratt & Lindley (1987) Biochem. J. 247, 369-375] suggests that the synergistic carbonate anion may be capable of behaving as a unidentate linkage to the Cu2+ in the dicupric complex. Data for Cu1.8COT are consistent with only three protein ligands bound to Cu2+, monodentate binding of the synergistic anion in one lobe and its bidentate binding in the other lobe. Such flexibility in the anion co-ordination may be a requirement for the uptake and release of metals by the transferrins.
 ...
PMID:X.a.f.s. studies of chicken dicupric ovotransferrin. 166 Feb 64

Uterine expression of lactoferrin (LF) during the preimplantation period and its regulation by the ovarian steroids estradiol (E2) and/or progesterone (P4) in ovariectomized adult mice were examined. Immunoblot detection of LF in uterine cell lysates demonstrated the presence of this protein from days 1-8 of pregnancy [day 1 (D1) = day of vaginal plug]. Immunoprecipitation of 35S pulse-labeled uterine proteins showed that the relative rate of LF synthesis was high on D1, but below the level of detection by D4. Immunolocalization of LF in uterine sections showed intense luminal and glandular epithelial staining on D1 and D2, and progressively decreased staining through D4. Immunoreactive protein was also detected in cells, primarily concentrated in the stroma. The relative number of these cells was greatest on D1 and decreased progressively to a low number by D4. These cells were morphologically similar to neutrophils, which are known to contain LF protein, but little or no LF mRNA. Northern blotting showed that uterine LF mRNA levels were very high on D1 and D2 of pregnancy and decreased to low, but detectable, levels by D4. In situ hybridization to uterine sections showed that LF mRNA was highly abundant only in glandular and luminal epithelial cells, and followed the same pattern as immunolocalization on D1-D4 in epithelial cells. These results document two sources of LF in the preimplantation mouse uterus: neutrophils and epithelial cells. The synthesis of LF in the uterus reflects the abundance of epithelial LF mRNA, which is high on the first 2 days of pregnancy. Neutrophils that contain LF are also abundant in the uterine stroma during this time. E2 and/or P4 regulation of uterine LF was examined. LF mRNA was rapidly induced by E2 in ovariectomized adult mice, and this mRNA was localized exclusively to epithelial cells. P4 had little effect on uterine LF mRNA levels, but antagonized the prolonged induction of this gene by E2. E2 induced the accumulation of immunoreactive LF in uterine epithelial cells and the appearance of numerous immunopositive neutrophils distributed throughout the uterine stroma. P4 also antagonized these effects. Thus, E2 regulates LF gene expression in uterine epithelial cells and causes the recruitment of neutrophils into the uterus. These results suggest that LF may play an important role in early pregnancy and that uterine LF gene expression is regulated by a balance between estrogen and P4.
Mol Endocrinol 1992 Jan
PMID:Lactoferrin in the mouse uterus: analyses of the preimplantation period and regulation by ovarian steroids. 173 63


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