Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A murine hybridoma has been obtained that produces a monoclonal antibody against the human transferrin receptor. In contrast to previously characterized monoclonal antibodies that recognize the transferrin receptor, this antibody, designated 42/6, blocks the binding of transferrin to its receptor and inhibits the growth of the human T leukemic cell line, CCRF-CEM, in vitro. Inhibition of cell growth was dose dependent, and as little as 2.5 micrograms of purified antibody per ml had a detectable effect, even though transferrin was present in the tissue culture medium in large molar excess. Cells grown in the presence of antibody for 7 days accumulated in S phase of the cell cycle. The addition of iron to antibody-treated cultures in the form of ferric complexes or ferrous sulfate did not overcome the growth inhibitory effects of the anti-transferrin-receptor antibodies. This result suggests that either transferrin is the only means by which CCRF-CEM leukemic cells can be provided with sufficient iron in vitro or that other factors in addition to iron starvation are involved in the antibody-mediated growth inhibition. The inhibition of cell growth by 42/6 monoclonal antibody suggests that monoclonal antibodies against proliferation-associated cell surface antigens, such as the transferrin receptor, may be useful pharmacological reagents to modify cell growth in vitro.
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PMID:Monoclonal antibody to transferrin receptor blocks transferrin binding and inhibits human tumor cell growth in vitro. 628 Jan 71

Native oligomers of three Pseudomonas aeruginosa outer membrane porin proteins and one Escherichia coli porin were demonstrated by using a chemical cross-linking technique. P. aeruginosa protein F, the major constitutive outer membrane porin, was cross-linked to dimers in outer membrane and whole-cell cross-linking experiments. Purified preparations of P. aeruginosa proteins F, D1 (glucose induced), and P (phosphate starvation induced) and E. coli protein PhoE (Ic) were also cross-linked to reveal dimers and trimers upon two-dimensional sodium dodecyl sulfate-polyacrylamide electrophoretic analysis. Cross-linking of protein F was abolished by pretreatment of the protein with sodium dodecyl sulfate, indicating that the cross-linked products were due to native associations in the outer membrane.
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PMID:Outer membrane porin proteins F, P, and D1 of Pseudomonas aeruginosa and PhoE of Escherichia coli: chemical cross-linking to reveal native oligomers. 630 36

Several mutants of Rhodopseudomonas sphaeroides defective in the derepression of the enzyme ribulose 1,5-bisphosphate carboxylase have been isolated by using the unstable Tn5 vectors pJB4JI and pRK340. Transpositional insertion mutants obtained with pJB4JI were demonstrated to be incapable of increasing ribulose 1,5-bisphosphate carboxylase/oxygenase levels when grown on butyrate-bicarbonate medium or under conditions of carbon starvation, whereas the wild-type strain increased activity four- to eightfold. When the wild-type strain was starved for carbon in the presence of chloramphenicol, no derepression was observed. Crude extracts from mutant and wild-type strains had distinct and consistent differences in protein content as observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Chromatographic evidence indicated that mutants were defective in the regulation of only one of the two forms of ribulose 1,5-bisphosphate carboxylase/oxygenase synthesized by R. sphaeroides.
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PMID:Isolation and partial characterization of Rhodopseudomonas sphaeroides mutants defective in the regulation of ribulose bisphosphate carboxylase/oxygenase. 631 4

Pyrophosphate (PPi) content of Escherichia coli is increased manyfold when the growth of the cells is limited by inhibition of the synthesis of nucleotides. The accumulated PPi is immediately degraded when inhibition is released and growth allowed to resume. Other tested nutritional deficiencies (starvation of carbon source, sulfate or an amino acid) fail to induce PPi accumulation.
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PMID:Accumulation of pyrophosphate in Escherichia coli. Relationship to growth and nucleotide synthesis. 631 80

GH specifically binds to receptors on the surface of adipocytes and produces a variety of biological effects in these cells. To gain insight into the nature of the GH receptors, [125I] human GH ([125I]hGH) was cross-linked to surface binding sites on intact rat adipocytes using the bifunctional reagent disuccinimidyl suberate. Plasma membranes were isolated, and after solubilization with sodium dodecyl sulfate (SDS), the proteins were subjected to electrophoresis on 5% or 7.5% polyacrylamide gel. Autoradiography of the 7.5% gels revealed three iodinated bands corresponding to apparent molecular weights of 56, 130, and more than 240 kilodaltons. The more than 240-kilodalton band contained approximately as much 125I as the 130-kilodalton species and about twice as much as the 56-kilodalton species. When run on the more porous 5% gel, the more than 240-kilodalton band resolved into two bands, corresponding to apparent molecular weights of 240 and 310 kilodaltons. Excess unlabeled human or bovine GH, but not ovine PRL, competed with [125I]hGH for binding and prevented the formation of all of the labeled bands. Treatment of the membranes and extracted proteins with dithiothreitol resulted in the generation of additional 130-kilodalton material at the expense of both the 310- and 240-kilodalton species, but failed to alter the amount of 125I that migrated with the 56-kilodalton species. The same pattern of labeling was seen regardless of whether protease inhibitors were present during isolation of membrane proteins or when membrane proteins were isolated under conditions that favored proteolysis, suggesting that the 56-kilodalton species is not a degradative product of the higher molecular weight species. When [125I]hGH was cross-linked to adipocytes in which total binding was decreased by hypophysectomy or starvation of the donor rats or by treatment of the cells with cycloheximide, there was a proportionate diminution in labeling of all species. It thus appears that the GH receptor contains a 130-kilodalton subunit, a portion of which is in disulfide linkage with higher molecular weight complexes and, in addition, contains a 56-kilodalton species. It cannot be determined from these studies if the various labeled protein complexes are components of a single or multiple classes of GH receptors in the adipocyte membrane.
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PMID:Covalent binding of growth hormone to surface receptors on rat adipocytes. 632 41

A cysteine metalloproteinase that degrades 125I-insulin B chain at neutral pH values was isolated from C3H mouse liver. The enzyme was partially purified from the 100,000g supernatant fraction by ammonium sulfate precipitation, DEAE-cellulose chromatography, and fast protein liquid chromatography. The molecular weight of the proteinase was estimated to be 190,000 by gel filtration on Sephadex G-200. Degradation of 125I-insulin B chain by the proteinase was inhibited by p-hydroxymercuribenzoate (PHMB) and iodoacetate (cysteine proteinase inhibitors) and by ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthroline (metalloproteinase inhibitors). The proteinase also degraded 125I-glucagon but did not hydrolyze 125I-insulin, leucine-2-naphthylamide, or several large proteins. Equivalent levels of EDTA- and PHMB-inhibitable 125I-insulin B chain-degrading activity were observed in the 100,000g supernatant fractions of brain, liver, lung, kidney, heart, and spleen from four mouse strains (C3H/HeN, CBA/J, ICR, and C57BL/6). High levels of 125I-insulin B chain-degrading activity were found in the particulate fraction of kidneys and lungs from these four mouse strains; these activities were inhibited by EDTA but not by PHMB. The activity of the soluble liver cysteine metalloproteinase was not altered in C3H mice treated ip with metal chelators, bacterial endotoxin, phenobarbital, dexamethasone, or insulin. Starvation for 24 or 48 hr and alloxan-induced diabetes diminished total activity of this enzyme in liver by about 50 and 30%, respectively. This soluble polypeptide-degrading enzyme appears to be ubiquitous in mice and to be regulated by nutritional conditions.
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PMID:A cysteine metalloproteinase from mouse liver cytosol. 643 52

alpha-Mannosidase from Dictyostelium discoideum is a heterogenous glycoprotein which is derived from a precursor as a result of proteolytic processing. Its oligosaccharides are phosphorylated and sulfated. We investigated the sulfation of the enzyme by means of pulse-chase labeling and specific immunoprecipitation followed by endoglycosidase H treatment and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The earliest detectable form of the precursor was shown to be glycosylated and sensitive to endoglycosidase H. With time some of its oligosaccharides were sulfated and became partially resistant to endoglycosidase H. In the same time period, the precursor was proteolytically cleaved, yielding four species with different molecular masses (46-58 X 10(3) daltons). When first generated each of these was sensitive to endoglycosidase H but with time the 54,000- and 58,000-dalton forms developed degrees of endoglycosidase H resistance. The fully mature cleaved forms all contained sulfate. Sulfate from pulse-labeled precursor could only be detected in two of the forms implying that sulfation of the others occurs either after precursor cleavage or before cleavage but subsequent to the pulse period. When secretion of precursor was triggered by starvation only the endoglycosidase H-resistant forms were secreted.
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PMID:Maturation of alpha-mannosidase in Dictyostelium discoideum. Acquisition of endoglycosidase H resistance and sulfate. 643 94

Three classes of mutants defective in the biosynthesis of the siderophore agrobactin were isolated from Agrobacterium tumefaciens A217 after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Class I mutants produced uniquely the catechol 2,3-dihydroxybenzoic acid, whereas classes II and III produced no detectable catechol. Class II differed from class III mutants in that exogenous 2,3-dihydroxybenzoic acid was utilized only by the former to synthesize agrobactin. Growth of strains B6 and A217, under iron starvation, led to enhanced production of several envelope proteins migrating in the 80,000-dalton range upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One mutant, defective in agrobactin iron utilization, lacked one of these proteins. This protein may represent a siderophore receptor or fragment or subunit thereof. With a single exception, all of the mutants obtained in this work were capable of initiating tumorous growth in sunflower plants and on carrot root disks, provided pTiB6806 was present. Comparison of the catechols produced by strain B6806 and its nononcogenic, Ti-plasmid-deficient derivative A217, indicated that the genes encoding agrobactin synthesis are not associated with the virulence plasmid of A. tumefaciens B6806. Analysis of gall tissue for agrobactin did not reveal the presence of this siderophore. Finally, citrate, an iron-carrier in plants, enhanced significantly the growth of the agrobactin-deficient mutants in a low-iron medium. These results suggest that the production of agrobactin in planta is not requisite to infection and that citrate may serve as an alternative carrier of iron for A. tumefaciens within the host.
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PMID:Relationship of siderophore-mediated iron assimilation to virulence in crown gall disease. 645 14

Anion transport across the red cell membrane has been measured as sulfate self-exchange flux (Ja) in fresh and metabolically depleted human red cells. Depletion of metabolic stores by a starvation of the cells decreases Ja by 50%. A similar effect was observed when ATP was acutely and selectively depleted by iodoacetamide. This inhibition was independent of the presence of calcium and reversible after metabolic rejuvenation of the cells. Ghosts prepared from fresh red cells exhibited the same value of Ja as fresh red cells. By contrast, ghosts prepared from depleted red cells exhibited a decrease in Ja which was reverted by a physiological concentration of ATP. The effect of ATP was dependent on its concentration (Km approximately 40 microM) and on the duration of the metabolic depletion: complete restoration of Ja was obtained only in ghosts prepared from red cells acutely depleted of ATP by a 2 h incubation with iodoacetamide. After a 20 h starvation, Ja restoration was never more than 80%. We postulate that ATP acts primarily through the phosphorylation of band 3 protein, the anion exchanger; it acts also through the stabilization of the normal organization of the membrane. This latter effect may involve the phosphorylation of membrane components, but also a direct interaction, as shown by the influence of other organic phosphates (2,3-diphosphoglycerate and inositol hexaphosphate) on Ja in the absence of ATP.
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PMID:Organic phosphates modulate anion self-exchange across the human erythrocyte membrane. 648 27

Antibodies specific for the Mr 65,000 (flavoprotein) and the Mr 28,000 subunits of the succinic dehydrogenase (SDH) of Bacillus subtilis were obtained. By using these antibodies it was shown that both subunits accumulated in the cytoplasm during 5-aminolevulinic acid starvation of a 5-aminolevulinic acid auxotroph. In the cytoplasm the subunits were not associated since they precipitated essentially independently of each other with subunit-specific antibody. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis the cytoplasmic subunits migrated identically with the corresponding subunits from the purified membrane-bound SDH complex. Cytoplasmic subunits were pulse-labeled with L-[35S]methionine during 5-aminolevulinic acid starvation. The labeled subunits bound to the membrane when heme synthesis was resumed and also when protein synthesis was blocked by chloramphenicol before readdition of 5-aminolevulinic acid. The experiments thus demonstrated a precursor relationship between cytoplasmic subunits and the subunits of the membrane-bound SDH complex. All SDH-negative mutants isolated so far carry mutations in the citF locus. None of the mutants was found to have either the Mr 65,000 or the Mr 28,000 SDH subunits in the membrane. Four citF mutants, however, contained both subunits in the cytoplasm. Three of these mutants lacked spectrally detectable cytochrome b558. The respective mutations mapped at one end of the citF locus. These results strongly support our previous suggestion that cytochrome b558 is (part of) a membrane binding site for SDH in B. subtilis.
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PMID:Biosynthesis and membrane binding of succinate dehydrogenase in Bacillus subtilis. 677 71


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