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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, on the basis of lectin binding and glycosidase digestion assays, we have suggested that N-acetyl-D-glucosamine residues (GlcNAc) are major structural components of both trophozoites and in vivo cysts of the intestinal parasite Giardia lamblia. In this report we confirm that GlcNAc is present both in trophozoites and in vitro cysts as assessed by lectin binding and glycosidase digestion assays, galactosyltransferase labeling, immunochemical analysis using antibodies specific for GlcNAc and its beta 1-4 oligomers, and by gas chromatography/mass spectrometry (GC/MS). The results show that wheatgerm agglutinin (WGA) binds specifically to intact trophozoites and in vitro cysts as well as to SDS-PAGE separated proteins. WGA binding to the separated proteins was markedly reduced after their digestion with N-acetyl-beta-D-glucosaminidase, supporting the conclusion that WGA is reacting with terminal beta-linked GlcNAc residues. Labeling of trophozoites and cysts by 3H-exogalactosylation with galactosyltransferase further confirmed the presence of terminal GlcNAc in both surface and intracellular glycoproteins. The presence of GlcNAc is also supported by microfluorometric analysis using antibodies to (GlcNAc)1, (GlcNAc)2, and (GlcNAc)3, which revealed a sugar-inhibitable binding of the antibody to live trophozoites. Finally, the presence of GlcNAc in both cysts and trophozoites was unequivocally confirmed by GC/MS analysis of detergent-extracted membranes and of glycoproteins isolated by affinity chromatography on WGA-agarose. GC/MS analysis also revealed mannose (Man), N-acetyl-D-galactosamine (GalNAc), fucose (Fuc), galactose (Gal), glucose (Glc) and N-acetylneuraminic acid (NANA) to be present in cysts. All these sugars were also present in trophozoites, except for GalNAc. The glycoproteins isolated by WGA affinity chromatography were 5- to 40-fold enriched in GlcNAc, further supporting the conclusion that WGA reacts with GlcNAc in Giardia. In summary, the data presented here provide biological and chemical evidence for GlcNAc in both cysts and trophozoites of G. lamblia and are consistent with previously published results from this and other laboratories.
Mol Biochem Parasitol 1990 Dec
PMID:N-acetyl-D-glucosamine is present in cysts and trophozoites of Giardia lamblia and serves as receptor for wheatgerm agglutinin. 212 47

A potential substrate of p60v-src in Rous sarcoma virus-transformed cells was found to be a 130-kilodalton (kDa) glycoprotein which binds to lectin-Sepharose and can be immunoprecipitated by an anti-phosphotyrosine antibody. This glycoprotein was shown to be distinct from the fibronectin receptor and a cellular protein phosphorylated in p60v-src immune complexes. The protein was a transmembrane protein localized in the plasma membrane and resistant to extraction with Triton X-100. The 130-kDa protein was also highly phosphorylated in cells transformed by Fujinami sarcoma virus or Y73 but not in cells infected with Rous sarcoma virus mutants that encode p60v-src lacking myristoylated N termini. Phosphorylation of this glycoprotein was temperature dependent in cells infected with temperature-sensitive mutants. The good correlation between its phosphorylation and morphological transformation, together with its relative abundance among phosphorylated proteins and its subcellular localization, suggests that phosphorylation of the 130-kDa glycoprotein is one of the primary events important for cell transformation by p60v-src and related oncogene products.
Mol Cell Biol 1990 Feb
PMID:A glycoprotein in the plasma membrane matrix as a major potential substrate of p60v-src. 215 25

Agglutination of human platelets by bovine von Willebrand factor (vWF) or by human vWF in the presence of ristocetin is inhibited by ADP and by several other platelet agonists but not by epinephrine. Vincristine, which causes a shape change by disrupting microtubules, neither inhibited agglutination nor blocked the effect of ADP. The action of ADP was blocked by ATP, by p-fluorosulfonylbenzoyladenosine, and by the thiol-reactive regents cytochalasin A and p-chloromercuribenzenesulfonate. In contrast to its effects on vWF, ADP enhanced agglutination induced by wheat germ lectin. ADP caused a small decrease in the number and affinity of binding sites for vWF on platelets, too small to explain the inhibition of agglutination. The ability of ADP and other agonists to inhibit agglutination appears to be related neither to inhibition of adenylate cyclase nor to the loss of their discoid shape but rather to the membrane changes that accompany the shape change.
Mol Pharmacol 1990 Feb
PMID:Effect of platelet activation on the agglutination of platelets by von Willebrand factor. 215 74

Crotalarin, the N-acetyl-D-galactosamine-binding blood group A-specific lectin from the seeds of Crotalaria striata was subjected to various chemical modifications in order to ascertain the amino acid residues responsible for its carbohydrate-binding property. Modification of lysine, cysteine and arginine residues did not affect the carbohydrate-binding activity of the lectin. However, modification of tyrosine residue and carboxy group of the acidic amino acids led to a complete loss of its activity, indicating the involvement of tyrosine and aspartic and glutamic acid in the saccharide-binding respectively. The hemagglutinating activity of the lectin was completely/almost completely lost by modification of tryptophan residues. The relative loss in hemagglutinating activity on modification of tryptophan residues indicate that one residue/molecule is required for the carbohydrate-binding activity of the lectin. Modification was not effective in the presence of D-galactose (0.2 M). A marked decrease in the fluorescence emission was found as the tryptophan residues of crotalarin were modified. The c.d. spectra showed the presence of an identical pattern of conformation in the native and modified lectins which confirms that the loss in activity was due to modification only. The effect of periodate oxidation on crotalarin showed loss of activity whereas action of enzymes retained most of the activity.
Mol Cell Biochem 1990 Aug 10
PMID:Chemical modification studies on a blood group A-specific lectin, crotalarin (Crotalaria striata) and its effect on hemagglutinating activity. 217 41

In adults, the alveolar epithelium is composed of types I and II cells which differ structurally and functionally although they appear to belong to the same cell lineage. Using cell-specific markers (type I cells, monoclonal antibody; type II cells, Maclura pomifera lectin [MPA]), we have determined when and in what pattern their binding sites occur during development of the fetal rat lung. Rather than first appearing on days 19 to 20, when morphogenesis of type I cells occurs and lamellar bodies provide positive identification of type II cells, the markers appeared on day 15 (for type I cell marker) and day 16 (for type II cell marker). The type I cell marker was widespread by day 17 and was sufficiently abundant to be detected on a Western blot. MPA binding appeared more gradually and was often found on isolated cells. On serial sections of day 20 lung, the markers appeared to be localized to the same cells. The early appearance of cell-specific markers suggests an early onset of the developmental program that leads to full differentiation of types I and II cells. Co-expression of both cell-specific markers suggest that fetal cell lineage may differ from the scheme proposed by others that type II cells serve as type I cell precursors during development.
Am J Respir Cell Mol Biol 1990 Jun
PMID:Expression of cell-specific markers for alveolar epithelium in fetal rat lung. 218 57

A frequently used mechanism for sperm-egg recognition in many species involves complementary protein-carbohydrate interaction. The usual paradigm includes complex glycoconjugates in reproductive tract fluids or on the eggs which are recognized by carbohydrate-binding proteins on the sperm surface. Various glycoconjugates are utilized in the steps of sperm capacitation, sperm binding to the egg extracellular matrix and vitelline membrane and induction of the acrosome reaction. Several types of complex glycoconjugates are involved in these processes, including proteoglycans, lactosaminoglycans, sulfated fucose-containing glycoconjugates, and glycoproteins. There appear to be some structural similarities between active glycoconjugates; they are large in molecular weight and complex, and they are often sulfated, fucosylated, and attached to a protein through serine or threonine residues. In some species, the protein core of the glycoconjugates also participates in the interaction by limiting the binding of carbohydrates to sperm only of the relevant species, likely by providing the proper steric arrangement for the interaction. In other cases the protein core seems to serve more as a crosslinker of the carbohydrate moieties. This review discusses the types of glycoconjugates implicated in fertilization and the complementary lectin-like proteins found on sperm.
Mol Reprod Dev 1990 Jun
PMID:Carbohydrates and fertilization in animals. 219 12

The Saccharomyces cerevisiae DPM1 gene product, dolichol-phosphate-mannose (Dol-P-Man) synthase, is involved in the coupled processes of synthesis and membrane translocation of Dol-P-Man. Dol-P-Man is the lipid-linked sugar donor of the last four mannose residues that are added to the core oligosaccharide transferred to protein during N-linked glycosylation in the endoplasmic reticulum. We present evidence that the S. cerevisiae gene DPM1, when stably transfected into a mutant Chinese hamster ovary cell line, B4-2-1, is able to correct the glycosylation defect of the cells. Evidence for complementation includes (i) fluorescence-activated cell sorter analysis of differential lectin binding to cell surface glycoproteins, (ii) restoration of Dol-P-Man synthase enzymatic activity in crude cell lysates, (iii) isolation and high-performance liquid chromatography fractionation of the lipid-linked oligosaccharides synthesized in the transfected and control cell lines, and (iv) the restoration of endoglycosidase H sensitivity to the oligosaccharides transferred to a specific glycoprotein synthesized in the DPM1 CHO transfectants. Indirect immunofluorescence with a primary antibody directed against the DPM1 protein shows a reticular staining pattern of protein localization in transfected hamster and monkey cell lines.
Mol Cell Biol 1990 Sep
PMID:The Saccharomyces cerevisiae DPM1 gene encoding dolichol-phosphate-mannose synthase is able to complement a glycosylation-defective mammalian cell line. 220 96

The use of conditional mutants as a genetic approach to study protein secretion in mammalian cells requires the isolation of a large number of mutants. Because a procedure for the direct selection of mutants with secretion defects is not available, their isolation depends upon the selective enrichment of mutant phenotypes in a cell population. We have devised an enrichment strategy in which rat hepatoma cells unable to replace surface membrane receptors of a plant lectin, concanavalin A, are resistant to the cytotoxic effects of this lectin when administered at a nonpermissive temperature. This treatment yields a population highly enriched in cells that demonstrate temperature-sensitive secretion. Therefore, this selection strategy has important application in isolating temperature-sensitive mutants for use in the study of the mammalian cell secretion pathway.
Somat Cell Mol Genet 1990 Jul
PMID:Selective enrichment for temperature-sensitive secretion mutants of mammalian cells using plant lectin, concanavalin A. 221 19

Cell interactions during mouse development have been shown to involve carbohydrate-containing macromolecules (glycoconjugates). We have therefore used a series of fluorescein-labelled synthetic glycoproteins to determine if mouse oocytes and zygotes also express sugar binding molecules (endogenous lectins) which might participate in such interactions. Unfertilized secondary oocytes did not express endogenous lectins at 4 degrees C but a low level of expression of fucose, mannose, and galactose-binding activity could be detected at 37 degrees C. In contrast, the zygote clearly expressed three classes of endogenous lectins, with preferential binding for i) fucose or mannose, ii) glucose or galactose, and iii) lactose. The expression of these lectins was much reduced at 4 degrees C and maximal binding at 37 degrees C was achieved only after 2 h incubation. We therefore conclude that a low level of endogenous lectin expression in the mouse oocyte is greatly enhanced after fertilisation and that, at both stages, expression, or the detection of expression, is markedly temperature dependent.
Mol Reprod Dev 1990 Aug
PMID:Mouse zygotes express endogenous lectins. 222 79

Cell surface carbohydrates, because of their demonstrated and potential structural diversity, have long been considered as excellent candidates for determinants of cell-cell recognition. Recently, a gene family has been identified, which encodes a series of three adhesion proteins (pnHR, ELAM-1, and GMP-140), designated as the LEC-CAMs. Each receptor participates in highly specific cell-cell recognition events within the blood vascular compartment. The LEC-CAMs share a high degree of sequence homology and the same organization of protein motifs, which includes a calcium-type lectin domain at the extracellular amino-terminus of each. In the case of the pnHR (peripheral lymph node homing receptor), the lectin domain has been shown to be central to the adhesive function of the receptor, i.e., lymphocyte attachment to high endothelial venules (HEV) of lymph nodes. The cognate ligand for the pnHR on HEV is a sialylated glycoprotein. Sialic acid is required for the adhesive function of this ligand, and preliminary evidence suggests that this requirement may also apply to the ligand for GMP-140. It is not clear as yet whether sialic acid contributes directly to recognition determinants of these ligands or has a modulating effect on their function. Given the extreme diversity of sialyloligosaccharides, the former possibility is very attractive. The LEC-CAM family joins the three families of already identified cell-cell adhesion molecules (integrins, cadherins, and superimmunoglobulins). It remains to be seen whether additional examples of highly specific cell recognition events rely on as yet unidentified LEC-CAMs or related lectin-like receptors.
Am J Respir Cell Mol Biol 1990 Nov
PMID:The LEC-CAMs: an emerging family of cell-cell adhesion receptors based upon carbohydrate recognition. 222 96


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