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)

It has been reported previously that some complex-type Asn-linked oligosaccharides contained in glycoproteins synthesized by Schistosoma mansoni adult males contain terminal galactosyl residues. We report here that extracts from S. mansoni adult male and female worms contain a beta 1,4-galactosyltransferase activity that transfers galactose from the donor substrate UDP-galactose to the acceptor substrate N-acetylglucosamine in a beta 1,4-linkage position to form the disaccharide Gal beta 1,4GlcNAc. In this respect the schistosome-derived activity is similar to that commonly found in mammalian tissues. The kinetic properties, however, of the common beta 1,4-galactosyltransferase activity in mammalian tissues are dramatically altered in the presence of the modifier protein alpha-lactalbumin, whereas the beta 1,4-galactosyltransferase activities in adult male and female schistosomes are not altered by this modifier. Overall, our results demonstrate that adult schistosomes contain a beta 1,4-galactosyltransferase activity and that it is unlike that commonly found in mammalian tissues.
Mol Biochem Parasitol 1990 Nov
PMID:Schistosoma mansoni contains a galactosyltransferase activity distinct from that typically found in mammalian cells. 212 77

The Nun protein of the lambdoid phage HK022 blocks lambda growth by terminating transcription at (or near) the lambda nut sites. An HK022 lysogen carrying a fusion of the lambda pR promoter and nutR site to a gal operon that lacks its own promoter is, therefore, Gal-. To characterize the target of Nun action, spontaneous Gal+ revertants of this strain were isolated and characterized. Two cis-acting mutations are located in the fusion and represent transversions of conserved nucleotides within the boxA sequence (CGCTCTTA) of nutR. One mutation, (CTCTCTTA), is identical with boxA5. The second, boxA16 (CGCTATTA), has not been reported previously. In the absence of Nun, both boxA mutants reduce gal expression. Analysis of in vivo fusion RNA indicates that the mutations increase termination at or near tR1, a rho-dependent lambda terminator located upstream from the fusion point. In contrast to the nutR+ fusion, Nun stimulates gal expression in the boxA mutants by suppressing transcription termination in the tR1 region. Nun antitermination, however, does not extend to distal terminators. The lambda N-function also suppresses termination at or near tR1 in the mutant fusions. N fails to suppress terminators distal to tR1 in the boxA5 fusion, but displays persistent antitermination activity in the boxA16 fusion. A similar reversal of Nun activity occurs when wild-type fusions are introduced into nusA1, nusB5 or nusE71 hosts. We therefore suggest that Nun and N can interact with RNA polymerase in the absence of wild-type boxA, nusA, nusB or nusE, but that the complex formed with mutant components differs functionally from wild-type.
J Mol Biol 1990 Apr 20
PMID:Lambda nutR mutations convert HK022 Nun protein from a transcription termination factor to a suppressor of termination. 213 72

Lymph node (LN) T cells from autoimmune MRL/MpJ-lpr/lpr (lpr) mice and control MRL/MpJ-(+)/+ (+/+) mice were compared as to glycosyl transferase activities involved in the biosynthesis of polylactosaminoglycans. The N-acetylglucosaminyl transferase (GlcNAc transferase) activity responsible for the extension of polylactosaminoglycans was assayed. The reaction products with this GlcNAc transferase were characterized by sequential glycosidase treatment and methylation analysis, and the enzyme was found to be classifiable as an UDP-GlcNAc:N-acetyllactosamine beta 1-3 GlcNAc transferase (polylactosamine extension enzyme). The activity of this GlcNAc transferase in T cells from enlarged LN of lpr mice was 3-6 times higher than that in T cells from +/+ mice. On the other hand, activated T cells from +/+ mice only showed about a 2-fold increase in the activity of the transferase, compared with that in resting T cells. B cells from +/+ mice also showed a significantly higher activity of the transferase than +/+ T cells, the enzyme activity being comparable to or slightly lower than that in lpr T cells. Furthermore, when the reaction mixture contained both UDP-GlcNAc and UDP-Gal as donors, extension of the Gal-GlcNAc residue was observed. These results indicated the biosynthetic basis for the abundance of polylactosaminoglycans in lpr T cells and normal B cells. We also found that lpr T cells exhibited significant UDP-GlcNAc:asialo-bovine submaxillary mucin GlcNAc transferase activity. Only weak activity of this enzyme was detected in +/+ resting and activated T cells, and B cells. This enzyme activity suggested the potential for polylactosaminoglycan formation on the mucin-type sugar chains on the surface of lpr T cells.
Mol Immunol 1990 Apr
PMID:Elevation of the activities of glycosyl transferases involved in polylactosaminoglycan biosynthesis in autoimmune MRL lpr/lpr mouse T cells. 214 66

The crystal structures of complexes of isolectins 1 and 2 of wheat germ agglutinin (WGA1 and WGA2) with N-acetylneuraminyl-lactose (NeuNAc-alpha(2-3)-Gal-beta(1-4)-Glc) have been refined on the basis of data in the 8 to 2.2 A resolution range to final crystallographic R-factors of 17.2% and 15.3% (Fo greater than 1 sigma), respectively. Specific binding interactions and water association, as well as changes in conformation and mobility of the structure upon ligand binding, were compared in the two complexes. The temperature factors (B = 16.3 A2 and 18.4 A2) were found to be much lower compared with those of their respective native structures (19 to 22 A2). Residues involved in sugar binding, dimerization and in lattice contacts exhibit the largest decreases in B-value, suggesting that sugar binding reduces the overall mobility of the protein molecules in the crystal lattice. The binding mode of this sialyl-trisaccharide, an important cell receptor analogue, has been compared in the two isolectins. Only one of the two unique binding sites (4 per dimer), located in the subunit/subunit interface, is occupied in the crystals. This site, termed the "primary" binding site, contains one of the five amino acid substitutions that differentiate WGA1 and WGA2. Superposition of the refined models in each of the independent crystallographic environments indicates a close match only of the terminal non-reducing NeuNAc residue (root-mean-square delta r of 0.5 to 0.6 A). The Gal-Glc portion was found to superimpose poorly, lack electron density, and possess high atomic thermal factors. In both complexes NeuNAc is stabilized through contact with six amino acid side-chains (Ser114 and Glu115 of subunit 1 and Ser62, Tyr64, Tyr(His)66 and Tyr73 of subunit 2), involving all NeuNAc ring substituents. Refinement has allowed accurate assessment of the contact distances for four hydrogen bonds, a strong buried non-polar contact with the acetamido CH3 group and a large number of van der Waals' interactions with the three aromatic side-chains. The higher affinity of N-acetylneuraminyl-lactose observed by nuclear magnetic resonance studies for WGA1 can be explained by the more favorable binding interactions that occur when residue 66 is a Tyr. The tyrosyl side-chain provides a larger surface for van der Waals' stacking against the NeuNAc pyranose ring than His66 and a hydrogen bond contact with Gal (C2-OH), not possible in WGA2.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1990 Oct 20
PMID:2.2 A resolution structure analysis of two refined N-acetylneuraminyl-lactose--wheat germ agglutinin isolectin complexes. 223 24

We describe two retroviral vector-based recombination substrate systems designed to assay for lymphoid VDJ recombinase activity in cultured cells. Both substrates incorporate a constitutive dominant marker gene (the simian virus promoter-driven neo gene) to allow selection of cells that stably integrate the substrate. Both substrates also include a second marker gene that becomes transcriptionally active only when inverted by a site-specific recombination event between flanking immunoglobulin variable-region gene segments. The first vector, similar in structure to previous retrovirus-based recombination substrates, utilizes the bacterial guanine-xanthine phosphoribosyltransferase gene (gpt) as its activatable marker; detection of inversion (VDJ recombinase activity) involves drug selection and Southern blotting analyses. We have used this vector to make a more extensive and quantitative survey of VDJ recombinase activity in B-lineage cell lines than has previously been performed with stable substrates, and we have compared our results with those of other studies that use transient recombination substrates. In the second vector, the activatable gene is the bacterial beta-galactosidase gene (lacZ). Detection for inversional activation of this gene is achieved by a fluorogenic assay, termed FACS-Gal, that detects beta-galactosidase activity in viable cells. The latter assay has the unique advantage of rapidly detecting cells that undergo recombination and also allows viable sorting of cells on the basis of the presence or absence of VDJ recombinase activity. We have used the lacZ vector to rapidly quantitate VDJ recombinase activity in B-lineage cell lines and compared the results with those obtained with the gpt vector. We have also used the lacZ vector to isolate variant pre-B-cell lines with low and high levels of VDJ recombinase activity.
Mol Cell Biol 1990 Apr
PMID:A novel fluorescence-based system for assaying and separating live cells according to VDJ recombinase activity. 232 7

Hybridoma generation, using specifically, maximally desialylated human blood group O erythrocytes (T RBC) as immunogen, and biochemical studies suggested the presence of immunogenic Tn epitopes. GalNAc alpha-O, on T RBC. We therefore investigated by immunochemical means whether or not Tn-specific epitopes immunoreactive with anti-Tn antibodies present in ordinary human sera occur on T RBC and on Thomsen-Friedenreich (T) antigen prepared from them. We did detect the Tn epitope with such antibodies, in addition to the T epitope, on isolated T antigen. T RBC absorbed specifically, under standard conditions, 25-60% of the heterogeneous anti-Tn antibody populations in ordinary human sera of appropriately adjusted titer score. The anti-Tn eluted from T RBC had scores ranging from 6.5 to 35% of those of the unabsorbed parent sera. The varying fine specificities of eluted anti-Tn were demonstrated by inhibition of Tn RBC agglutination with putative haptens and antigens. Tn-specific haptens and antigens were the most powerful inhibitors. Depending on the serum used to prepare the anti-Tn eluates, the antibodies could be divided into those that were inhibited well exclusively by GalNAc alpha-O derivatives and those that were also inhibited by Gal, notably by Gal alpha-O derivatives and more strongly by GalNAc and Me-alpha-GalNAc. In the two reciprocal hemagglutination inhibition systems used, Tn-specific haptens were considerably more active than the T-hapten Gal beta 1----3GalNAc alpha-O, and desialylated ovine submaxillary mucin (AS-OSM) had higher activity than T antigen. Inhibition of Tn RBC agglutination by haptens was uniformly more efficient than that of T RBC; this is, at least in part, due to the much higher negative charge of Tn as opposed to T RBC. In microprecipitin tests, Helix pomatia lectin was nearly as powerful a precipitin of T antigen as of AS-OSM. The importance of the terminal GalNAc alpha of T antigen for its precipitation with the Helix lectin was demonstrated by the very high and virtually exclusive inhibitory activity of Me-alpha-GalNAc and GalNAc. Our findings may contribute to comprehension of the significance of uncovered Tn in most carcinomas, and the role of anti-Tn as a "natural" anti-carcinoma antibody. They may also help illuminate the rare heterozygous, autosomal, apparently premalignant spot mutation that leads to Tn RBC in vivo.
Mol Immunol 1985 Nov
PMID:Tn epitopes, immunoreactive with ordinary anti-Tn antibodies, on normal, desialylated human erythrocytes and on Thomsen-Friedenreich antigen isolated therefrom. 241 12

Single crystals of Maclura pomifera agglutinin, a seed lectin from the Moraceae family, complexed with the disaccharide Gal beta 1-3GalNAc have been obtained by the method of vapor diffusion with Li2SO4 as precipitant at pH 4.5. The crystals belong to the trigonal space group P3(1)21 or P3(2)21, with a = b = 67.4 A, c = 149.3 A. They contain two subunits per asymmetric unit and diffract beyond 2.7 A. This and other evidence indicate that both this lectin and the Artocarpus integrifolia lectin, jacalin, have dimeric structures rather than the tetrameric structures previously proposed.
J Mol Biol 1989 Dec 05
PMID:Crystallization and preliminary X-ray diffraction studies of the complex of Maclura pomifera agglutinin with the disaccharide Gal beta 1-3GalNAc. 261 42

Gal repressor inhibits transcription by binding to two operators (OE and OI) in the gal operon. By ethylating DNA, we have identified 23 phosphate groups (11 on OE and 12 in OI) in the DNA backbone of gal operators that when ethylated interfere with repressor binding. By inference, either (1) such a phosphate is contacted or closely approached by Gal repressor, or (2) the structure of DNA generated by ethylation of such a phosphate, although not a site of direct contact, is not compatible with repressor binding. Within an operator, these phosphates are arranged with a perfect symmetry aligned with the operator dyad symmetry, indicating that each half-symmetry is contacted by a subunit of repressor dimer. Unlike in many other similar DNA-protein systems, the same phosphates in the gal operator are distributed around a B-form of DNA helix cylinder covering greater than 180 degrees. Models have been proposed to describe the disposition of the Gal repressor-operator complex, which would explain the layout of the participating phosphate groups around the surface of the DNA helix. We have discussed two ways by which Gal repressor can induce structural changes in DNA.
J Mol Biol 1989 Jul 20
PMID:Effect of ethylation of operator-phosphates on Gal repressor binding. DNA contortion by repressor. 267 89

The 43 kDa human chorionic gonadotropin (hCG) (SP-hCG) was purified from human placenta and analyzed for sugar moieties. The low hexosamine content suggests that SP-hCG probably lacks O-linked sugar chains in the beta-subunit and incompletely formed N-linked sugar chains in the alpha- and beta-subunits. In the present study SP-hCG was hydrolyzed with various glycosidases. Treatment of hCG or SP-hCG with O-glycan peptide hydrolase increased the mobility of asialo-hCG beta in reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) while that of SP-hCG beta was unaffected, indicating that SP-hCG beta does not contain NeuNAc-Gal-GalNAc unit. Alpha-Mannosidase and endoglycosidase H hydrolyzed mannose and the high mannose-GlcNAc moieties, respectively, from alpha- and beta-subunits of SP-hCG, but not from the subunits of authentic hCG. Glycopeptidase F hydrolyzed completely the N-linked sugar chains from SP-hCG subunits, producing alpha- and beta-subunits with estimated Mr of 15,000 and 18,500, respectively. The biological activity of purified SP-hCG is about 50-80% of highly purified authentic hCG. In an in vitro system SP-hCG increased cAMP accumulation and testosterone production by rat Leydig cells to the same levels as that induced by hCG. However, the biological activity of SP-hCG was markedly reduced, following treatment with endoglycosidase H or alpha-mannosidase. To attain the level of testosterone production equivalent to that induced with untreated SP-hCG, 10-20 times higher dose of treated SP-hCG was required. On the other hand, cAMP accumulation induced with treated SP-hCG even at a very high concentration was substantially lower than that attained with untreated SP-hCG. In conclusion, the mannose moieties are essential structural components of the hormone in stimulating cAMP accumulation and steroidogenesis by rat Leydig cells.
Mol Cell Endocrinol 1989 Mar
PMID:Carbohydrate moieties of small placental hCG: requirement of mannose structure for biological activity. 274 19

As previously reported, incubation of liver dolichol-P, UDP-[14C]Gal, and a particulate preparation of Acetobacter xylinum leads to the synthesis of dolichol-P-[14C]Gal (P. Romero, R. Garcia, and M. Dankert (1977) Mol. Cell. Biochem. 16, 205-212). It is now reported that upon incubation of the latter with rat liver microsomes, [14C-galactose]-Gal1Man9GlcNAc2-P-P-dolichol and [14C-galactose]Gal1Glc1Man9GlcNAc2-P-P-dolichol are formed. The galactosyl residues appeared to be (1,3)-linked in the same positions as the glucose units in the respective physiological compounds. No lipid-linked Gal1Glc2Man9GlcNAc2 was formed, thus strongly suggesting the presence of at least two dolichol-P-Glc:dolichol-P-P-oligosaccharide glucosyltransferases, only one of which is able to use dolichol-P-Gal as substrate. Incubation of the galactosylated dolichol-P-P derivatives with rat liver microsomes led to the transfer of the oligosaccharides to microsomal proteins. No endogenous, membrane-bound glycosidases were able to remove the galactose residues but mannose units were excised by endogenous neutral mannosidases.
 ...
PMID:A biochemical chimera suggesting the existence of at least two dolichol-P-glucose:dolichol-P-P-oligosaccharide glucosyltransferases. 282 24


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