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Query: UNIPROT:P06889 (Mol)
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To determine the relationship between invertase gene expression and glucose and fructose accumulation in ripening tomato fruit, fruit vacuolar invertase cDNA and genomic clones from the cultivated species, Lycopersicon esculentum cv. UC82B, and a wild species, Lycopersicon pimpinellifolium, were isolated and characterized. The coding sequences of all cDNA clones examined are identical. By comparison to the known amino acid sequence of mature L. esculentum fruit vacuolar invertase, a putative signal sequence and putative amino-terminal and carboxy-terminal propeptides were identified in the derived amino acid sequence. Of the residues 42% are identical with those of carrot cell wall invertase. A putative catalytic site and a five-residue motif found in carrot, yeast, and bacterial invertases are also present in the tomato sequence. Minor differences between the nucleotide sequences of the genomic clones from the two tomato species were found in one intron and in the putative regulatory region. The gene appears to be present in one copy per haploid genome. Northern analysis suggests a different temporal pattern of vacuolar invertase mRNA levels during fruit development in the two species, with the invertase mRNA appearing at an earlier stage of fruit development in the wild species. Nucleotide differences found in the putative regulatory regions may be involved in species differences in temporal regulation of this gene, which in turn may contribute to observed differences in hexose accumulation in ripening fruit.
Plant Mol Biol 1993 Feb
PMID:Isolation and characterization of fruit vacuolar invertase genes from two tomato species and temporal differences in mRNA levels during fruit ripening. 809 64

Trypanosoma brucei brucei (EATRO-164) contains a tandem array of six genes encoding a glucose transporter, THT1 (trypanosome hexose transporter), followed by five genes encoding a second isoform, THT2. Two distinct clusters containing THT1 and THT2 genes have been identified in the EATRO-164 clone and in most other African trypanosome clones analyzed. Analysis of progeny from crosses between clones of T. b. brucei displaying polymorphism in THT1 copy number per cluster suggests that the two clusters of THT genes are present on homologous chromosomes. In addition, analysis of 30 African trypanosome clones revealed a high degree of polymorphism in THT1 copy number per cluster. Sequence comparison of five THT1 and two and one-half THT2 unit repeats, present within a 20-kb region, provided information about the genesis and evolution of the THT multigene family. The most divergent regions between THT1 and THT2 unit repeats probably arose from insertion of DNA fragments into an ancestral THT region. Genes of each of the different families are almost identical, and there are large regions of identity shared between THT1 and THT2 members. A mosaic copy containing most of a THT1 gene with the 3' extremity of a THT2 gene is found within the cluster. These results suggest that THT1 and THT2 arose by modification (insertion, mutation, or conversion) of duplicated ancestral genes. Functional constraints and homologous recombination may be evoked to explain the maintenance of the conserved sequences of THT1 and THT2.
Mol Biol Evol 1994 Mar
PMID:African trypanosome glucose transporter genes: organization and evolution of a multigene family. 817 Mar 63

High levels of L-lysine were used to select for resistant variants of Chinese hamster ovary (CHO-K1) cells. Surviving colonies were screened for altered lysine transport and two with reduced uptake were picked. Clone CH-Kr, derived from the more severely affected colony, was analyzed in detail. In starved cells the Vmax of lysine uptake in CH-Kr was half that of CHO while Km was unaltered. The intracellular pool of lysine, a substrate of cationic amino acid transport system y+, was significantly lower in CH-Kr. However, transport and pools of other amino acids, which are not substrates of y+, were also reduced in CH-Kr, as was the internal sodium concentration, while hexose import was increased. It appears that the mutation in CH-Kr is pleiotropic, affecting some general aspects of amino acid transport.
Somat Cell Mol Genet 1993 Jul
PMID:Selection of a lysine-resistant CHO-K1 mutant with reduced amino acid transport through multiple systems. 821 77

A tandemly arranged multigene family encoding putative hexose transporters in Trypanosoma brucei has been characterized. It is composed of two 80% homologous groups of genes called THT1 (six copies) and THT2 (five copies). When Xenopus oocytes are microinjected with in vitro-transcribed RNA from a THT1 gene, they express a glucose transporter with properties similar to those of the trypanosome bloodstream-form protein(s). This THT1-encoded transport system for glucose differs from the human erythrocyte-type glucose transporter by its moderate sensitivity to cytochalasin B and its capacity to transport D-fructose. These properties suggest that the trypanosomal transporter may be a good target for antitrypanosomal drugs. mRNA analysis revealed that expression of these genes was life cycle stage dependent. Bloodstream forms express 40-fold more THT1 than THT2. In contrast, procyclic trypanosomes express no detectable THT1 but demonstrate glucose-dependent expression of THT2.
Mol Cell Biol 1993 Feb
PMID:Differential regulation of two distinct families of glucose transporter genes in Trypanosoma brucei. 842 81

In purified pancreatic islet B cells, a rise in D-glucose concentration from 2.8 to 16.7 mM increased the production of both 14CO2 from D-[3,4-14C]glucose and 3HOH from D-[5-3H]glucose to a much greater relative extent than in purified non-B islet cells. Moreover, the paired ratio between D-[3,4-14C]glucose oxidation and D-[5-3H]glucose utilization was significantly increased, as a result of the rise in hexose concentration, in purified B cells, but not so in purified non-B cells. It is proposed, therefore, that a preferential stimulation by D-glucose of oxidative relative to total glycolysis represents an intrinsic attribute of insulin-producing cells, as distinct from other endocrine islet cells.
Biochem Mol Biol Int 1993 Mar
PMID:Preferential stimulation by D-glucose of oxidative glycolysis in pancreatic islets: comparison between B and non-B cells. 848 64

Sedimentation equilibrium measurements and scanning transmission electron microscopy (STEM) mass mapping of the extracellular, hexagonal bilayer hemoglobin (HBL Hb) of the earthworm Lumbricus terrestris provided masses of 3.41 to 3.66 MDa and 3.56 (+/- 0.13) MDa, respectively. The Hb also contains 57.2 (+/- 6.0) moles of tightly bound Ca per mole of protein. The Hb and its subunits obtained by dissociation, in native, dehemed and reduced carbamidomethylated forms, were subjected to electrospray ionization mass spectroscopy (ESI-MS). Maximum entropy deconvolution identified three groups of peaks, at approximately 16 kDa, 24 to 32 kDa and approximately 53 kDa corresponding to the monomer subunit M (globin chain d), four linker subunits and the disulfide-bonded trimer T (globin chains a + b + c). Subunit M consisted of three components, d1 (15, 992.4), d2 (15, 978.0) and d3 (15, 962.1) (+/- 1.0 Da), with relative intensities 1.0:5:0.3, respectively. Subunit T consisted of four major components, T1 (52, 922.6), T2 (52, 760.0), T3 (52, 598.5) and T4 (52, 435.4) (+/- 4.0 Da), with relative intensities 0.6:1.0:0.2:0.7, respectively. ESI-MS of carbamidomethylated T, demonstrated that, unlike chains b (16, 254.4) and c (17, 289.2), chain a exists as a series of four, hexose-connected, glycosylated isoforms, a1 to a4 (19, 389.9, 19, 227.4, 19, 065.3 and 18, 902.9) (+/- 1.0 Da). The mass differences between the deglycosylated chain a (17, 524.0) and a1 to a4 correspond to glycan side-chains (GlcNAc)2 (Man)n (n = 6 to 9). Four groups of peaks were observed in the 24 to 32 kDa region. Linkers L1a (27, 540.8) and L1b (27, 702.4) (+/- 2.0 Da) are isoforms of L1 (25, 837.5 in N-deglycosylated Hb) with glycan side-chains (GlcNAc)2 (Man)n (n = 8,9). Linkers L2 (32, 104.3 (+/- 5.0) Da) and L3 (24, 912.9 (+/- 2.0) Da) occur as single species. Linkers L4a to L4c (24, 019.0, 24, 102.3 and 24, 169.9) (+/- 2.0 Da) with relative intensities 1.0:0.8:0.8, have not been identified previously. From ESI-MS relative intensities, L1:L2:L3:L4 = 0.6:0.4:1.0:0.5 and globin linker = 0.78:0.22. HPLC of Lumbricus Hb provided a globin linker = 0.73:0.27 (+/- 0.02) and a heme content of 2.52 (+/- 0.14) wt%. A model is proposed for the HBL structure, wherein 12 213.4 kDa dodecamers (144 globin chains, 2561 kDa) decorate a hexagonal framework of 36 linker chains (12L1 + 6L2 + 12L3 + 6L4) to provide a total mass of 3.531 MDa, each dodecamer being in contact with three linker subunits.
J Mol Biol 1996 Jan 12
PMID:Mass spectrometric composition and molecular mass of Lumbricus terrestris hemoglobin: a refined model of its quaternary structure. 856 63

Intraperitoneal injections of the nicotinamide antagonist 6-amino-nicotinamide (6-AN) were used to determine if there are regional differences in putative glial energy metabolism between the developing and adult rat CNS. 6-AN shuts down the hexose monophosphate pathway, which is used preferentially by astrocytes and oligodendrocytes. These cells subsequently undergo cytotoxic edema and cell death. Adult rats and pups ranging in age from 7 to 31 d received a single injection of 6-AN and were sacrificed after 24 h. As demonstrated wit immunocytochemical staining for the astroglia-specific markers GFAP and S-100 beta, the 7-9-d-old animals exhibited a uniform appearance with edematous glial cells located throughout the CNS. However, with advancing age, a consistent pattern of progressively decreasing amounts of injured glia, which has not been previously described, occurred in cerebral and cerebellar structures. After 3 wk postnatal, the adult pattern was manifested in which glial degeneration occurred only in specific regions of the spinal cord, cerebellum, medulla, and thalamus, whereas the remainder of the CNS appeared normal. The results suggest the presence of heterogeneous populations of glia whose preferred use of the hexose monophosphate pathway is predicated on both the age of the animal and their location in the CNS.
Mol Chem Neuropathol 1995 Oct
PMID:Age-dependent susceptibility of CNS glial populations in situ to the antimetabolite 6-aminonicotinamide. 857 44

Single pancreatic beta-cells exposed to D-glucose in the absence or presence of L-leucine and to the amino acid in the absence or presence of either the monomethyl ester of succinic acid (SME) or the dimethyl ester of glutamic acid (GME) were examined in a reverse hemolytic plaque assay for insulin release. At a D-glucose concentration of 11.1 mM, plaque-forming cells amounted to 84.8 +/- 1.0% including 11.4 +/- 4.1% of cells forming large plaques. These percentages were not increased by the incorporation of L-leucine (5 mM) into the incubation medium despite the fact that the amino acid, when tested in the absence of D-glucose, caused sizeable secretory activity. When the secretory response evoked by L-leucine was increased by either SME (10 mM) or GME (3 mM), marked heterogeneity of individual beta-cells in terms of both the occurrence and magnitude of hemolytic plaques was again observed. These findings argue against the view that the heterogeneity in secretory behavior of isolated purified beta-cells can be accounted for solely by differences in hexose metabolism as conceivably attributable to individual variations in glucokinase activity.
Biochem Mol Med 1995 Apr
PMID:Functional heterogeneity of single pancreatic beta-cells stimulated by L-leucine and the methyl ester of succinic or glutamic acid. 858 58

The facilitative glucose transporters are a family of proteins responsible for the transmembrane transport of glucose and other hexose sugars (1,2). In mammals, the seven glucose transporter isoforms display a characteristic tissue distribution reflecting the physiological requirement and metabolism of glucose. This report describes the isolation and sequencing of the full length ovine GLUT-3 cDNA and the tissue distribution of ovine GLUT-1 and GLUT-3 mRNA. The ovine GLUT-3 cDNA is 3854 base pairs and the coding nucleotides show 82% and 79% homology with the human and mouse GLUT-3 sequences respectively. In addition, a reverse transcriptase-polymerase chain reaction strategy is described for the rapid isolation of mammalian cDNA subclones for GLUT-1, GLUT-2 and GLUT-4. This method has been used to isolate the corresponding ovine subclones.
Biochem Mol Biol Int 1995 Sep
PMID:Isolation of cDNAs and tissue specific expression of ovine glucose transporters. 865 93

Cloning of the rfb genes of Shigella flexneri 2a into Escherichia coli K-12 strain DH1 results in the synthesis of lipopolysaccharides (LPS) with an O-antigen chain having type antigen IV and group antigens 3,4. During genetic studies of these rfb genes in E. coli K-12, we observed that strains harbouring plasmids with certain mutations (inversion and transposon insertions) which should have blocked O-antigen synthesis nevertheless still produced LPS with O-antigen chains. These LPS migrated differently on silver-stained SDS-polyacrylamide gels, compared with the LPS produced by wild-type rfb genes, and the group 3,4 antigens were barely detectable, suggesting that the O-antigen was altered. Investigation of the genetic determinants for production of the altered O-antigen/LPS indicated that: (i) these LPS are produced as a result of mutations which are either polar on rfbF or inactivate rfbF; (ii) the rfbX gene product (or a similar protein in the E. coli K-12 rfb region) is needed for production of the altered O-antigen in the form of LPS; (iii) the rfbG gene product is required for the production of both the parental and altered LPS; (iv) the dTDP-rhamnose biosynthesis genes are required. Additionally, an E. coli K-12 gene product(s) encoded outside the rfb region also contributes to production of the O-antigen of the altered LPS. An antiserum raised to the altered LPS from strain DH1(pPM2217 (rfbX::Tn1725)) was found to cross-react with nearly all S. flexneri serotypes, and with the altered LPS produced by other DH1 strains harbouring plasmids with different rfb mutations, as described above. The reactivity of the altered LPS with a panel of monoclonal antibodies specific for various S. flexneri O-antigen type and group antigens demonstrated that their O-antigen components were closely related to that of S. flexneri serotype 4. The RfbF and RfbG proteins were shown to have similarity to rhamnose transferases, and we identified a motif common to the N-termini of 6-deoxy-hexose nucleotide sugar transferases. We propose that the E. coli K-12 strains harbouring the mutated S. flexneri rfb genes produce LPS with a hybrid O-antigen as a consequence of inactivation of RfbF and complementation by an E. coli K-12 gene product. Analysis of the genetic and immunochemical data suggested a possible structure for the O-antigen component of the altered LPS.
Mol Microbiol 1995 Oct
PMID:Lipopolysaccharide with an altered O-antigen produced in Escherichia coli K-12 harbouring mutated, cloned Shigella flexneri rfb genes. 870 41


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