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Query: UNIPROT:P06889 (Mol)
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Mannan-binding proteins found in the liver and serum of several vertebrate species are supposed to play an important role in the intracellular transport of glycoproteins, as well as in several protective reactions including complement activation and elimination of various pathogens. To study these protective functions at molecular level it is necessary to understand the fine oligosaccharide specificity and mutual relation among various forms of these soluble lectins. We have isolated mannan-binding protein as peripheral membrane proteins of porcine lymphocytes. This lectin was purified to homogeneity and shown to possess many properties in common with the well studied rat liver proteins (mol. mass, subunit composition and general organization of the molecule). Binding studies performed with three series of defined oligosaccharides (high mannose, hybrid type, and complex) on native lectin molecules as well as isolated carbohydrate-binding domains revealed distinctive features of this mannan-binding protein, including its impaired ability to bind the oligosaccharide ligand after reduction and decyclization at core N-acetyl-D-glucosamine 1.
Mol Immunol 1992 Dec
PMID:Localization and characterization of the carbohydrate-binding site of the porcine lymphocyte mannan-binding protein. 145 63

The nodABC genes of rhizobia are essential for the synthesis of lipo-oligosaccharidic (N-acylated chitin oligomers) nodulation signals. nodC gene products from Rhizobium, Bradyrhizobium, and Azorhizobium exhibit extensive homology with chitin synthases, suggesting that the NodC proteins are involved in the synthesis of the chitin oligomer backbone by catalyzing the beta-1,4-linkage between N-acetyl-D-glucosamine residues.
Mol Plant Microbe Interact
PMID:The Rhizobium, Bradyrhizobium, and Azorhizobium NodC proteins are homologous to yeast chitin synthases. 147 21

A structure of the trisaccharide 2-acetamido-2-deoxy-D-muramic acid-beta (1----4)-2-acetamido-2-deoxy-D-glucose-beta (1----4)-2-acetamido-2-deoxy-D-muramic acid (NAM-NAG-NAM), bound to subsites B, C and D in the active-site cleft of hen egg-white lysozyme has been determined and refined at 1.5 A resolution. The resulting atomic co-ordinates indicate that the NAM residue in site D is distorted from the full 4C1 chair conformation to one in which the ring atoms C-1, C-2, O-5 and C-5 are approximately coplanar, and the hydroxymethyl group is positioned axially (a conformation best described as a sofa). This finding supports the original proposals that suggested the ground-state conformation of the sugar bound in site D is strained to one that more closely resembles the geometry required for the oxocarbonium-ion transition state, the next step along the reaction pathway. Additionally, detailed analysis at 1.5 A resolution of the environments of the catalytic residues Glu35 and Asp52 provides new information on the properties that may allow lysozyme to promote the stabilization of an unusually long-lived oxocarbonium-ion transition state. Intermolecular interactions between the N-acetylmuramic acid residue in site D and the lysozyme molecule that contribute to the saccharide ring distortion include: close packing of the O-3' lactyl group with a hydrogen-bonded "platform" of enzyme residues (Asp52, Asn46, Asn59, Ser50 and Asp48), a close contact between the hydroxymethyl group of ring D and the 2'-acetamido group of ring C and a strong hydrogen-bonded interaction between the NH group of Val109 and O-6 of ring D that stabilizes the observed quasi-axial orientation of the -CH2OH group. Additionally, the structure of this complex shows a strong hydrogen bond between the carboxyl group of Glu35 and the beta-anomeric hydroxyl group of the NAM residue in site D. The hydrogen-bonded environment of Asp52 in the native enzyme and in the complex coupled with the very unfavorable direction of approach of the potential carboxylate nucleophile makes it most unlikely that there is a covalent glycosylenzyme intermediate on the hydrolysis pathway of hen egg-white lysozyme.
J Mol Biol 1991 Jul 20
PMID:Lysozyme revisited: crystallographic evidence for distortion of an N-acetylmuramic acid residue bound in site D. 185 65

A high affinity tritiated azido-diphenylpiperazine derivative, 3-azido[3H]GBR-12935, was synthesized as a potential photoaffinity probe of the dopamine transporter. Initially, the reversible binding of 3-azido[3H]GBR-12935 to crude synaptosomal membranes from the rat striatum was characterized. Specific binding was sodium dependent and inhibited by a variety of drugs that are known to potently inhibit dopamine uptake. Other neurotransmitter uptake inhibitors, as well as cis-flupenthixol, a potent inhibitor of [3H]GBR-12935 binding to piperazine binding sites, failed to inhibit specific binding at concentrations of less than or equal to 10 microM. A good correlation was observed between the relative potencies of these drugs in inhibiting dopamine uptake into synaptosomes and in inhibiting specific 3-azido[3H]GBR-12935 binding to rat striatal membranes (r = 0.95, p less than 0.01). These data suggest that 3-azido[3H]GBR-12935, like other diphenylpiperazines such as [3H]GBR-12935 and [3H]GBR-12909, binds primarily to the dopamine transporter under defined assay conditions. After UV photolysis of crude synaptosomal membranes preincubated with 3-azido[3H]GBR-12935 (1-2 nM), a single radiolabeled polypeptide with an apparent molecular mass of 80 kDa was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Photoincorporation of 3-azido[3H]GBR-12935 into this polypeptide was inhibited selectively by compounds that inhibit the uptake of dopamine (but not other biogenic amines) and was completely dependent on the presence of Na+. No photolabeled proteins were observed when cerebellar membranes were substituted for striatal membranes. Essentially complete adsorption of the radiolabeled 80-kDa polypeptide to wheat germ agglutinin and elution with N-acetyl-D-glucosamine strongly suggest that the dopamine transporter polypeptide photolabeled by 3-azido[3H]GBR-12935 is glycosylated.
Mol Pharmacol 1991 Apr
PMID:Photoaffinity labeling of the dopamine reuptake carrier protein with 3-azido[3H]GBR-12935. 201 46

Chitinase, which catalyzes the hydrolysis of the beta-1,4-N-acetyl-D-glucosamine linkages of the fungal cell wall polymer chitin, is involved in inducible defenses of plants. A basic chitinase genomic sequence was isolated from a rice (Oryza sativa L.) genomic library using a bean chitinase gene fragment as a probe. The complete nucleotide sequence of the rice chitinase RCH10 gene was determined, and shown to contain an open reading frame with no introns, encoding a polypeptide of 336 amino acids. This polypeptide consists of a 21 amino acid signal peptide, a hevein domain, and a chitinase catalytic domain. The RCH10 gene has 63% identity at the nucleotide level and 75% identity at the amino acid level with chitinase genes from dicotyledonous plants such as bean, potato, and tobacco. A gene fusion of trpE and the coding region of RCH10 expressed in Escherichia coli gave a product that reacted with antiserum to bean chitinase, confirming the identity of RCH10 as a rice chitinase gene. Primer extension analysis identified two transcription start sites 53 bp and 55 bp upstream from the translation initiation codon. The 5' flanking region contains TATA and CAAT boxes, and the 3' region contains an AATAA polyadenylation signal. Southern blot hybridization indicated that there is a family of chitinase genes in the rice genome. Northern blot analysis showed that the RCH10 chitinase gene is induced in suspension cultured cells by a fungal cell wall elicitor. Rice chitinase transcripts accumulate to a high level in roots, but only low levels are found in stem and leaf tissue.
Mol Gen Genet 1991 Apr
PMID:Isolation and characterization of a rice gene encoding a basic chitinase. 203 21

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

During development the content of mesenchymal glycosaminoglycans (GAG) undergoes prominent changes, currently considered to act as regulatory signals in the epithelial-mesenchymal interactions. The factors involved in controlling GAG composition are as yet completely unknown. Lysosomal enzymes play a key role in GAG turnover. A possible mechanism for regulating GAG content could therefore be linked to developmental modulation of lysosomal glycosidases activity. We have examined the activity of the beta-N-acetyl-D-glucosaminidase (EC 3.2.1.30; a lysosomal hydrolase cleaving glycosidic linkage of the non-reducing terminal beta-N-acetyl-D-glucosamine residues) in chick embryo skin and lung (rudiments whose GAG composition has previously been studied) at various embryonic stages. Determinations were carried out on whole organs as well as on primary cultures of fibroblasts obtained from the two rudiments. beta-N-acetyl-D-glucosaminidase activity varied greatly during development, and it was significantly different in embryonic skin and lung tissues at various incubation days. In cultured fibroblasts, the enzymatic activity varied at different incubation days correlating with the in vivo data. Developmental changes of beta-N-acetyl-D-glucosaminidase paralleled mesenchymal GAG pattern both in vivo and in vitro. Our results, therefore, support the possibility that lysosomal enzymes could be involved in the regulation of mesenchymal GAG content during development.
Cell Mol Biol 1989
PMID:Beta-N-acetyl-D-glucosaminidase activity in embryonic chick skin and lung tissue and cultured fibroblasts. 273 Nov 94

[3H]beta-funaltrexamine ([3H]beta-FNA) bound irreversibly to bovine striatal membranes. Naloxone inhibited the irreversible binding of 5 nM [3H]beta-FNA in a dose-dependent manner and maximally inhibited this binding at approximately 1 microM. Thus, the specific irreversible binding of [3H]beta-FNA to opioid receptors was defined as that which could be inhibited by 1 microM naloxone. This specific irreversible binding of [3H]beta-FNA was characterized. Exclusion of Na+ from the incubation medium reduced the specific binding of [3H]beta-FNA, and Na+ could be substituted by Li+ but not by K+, Cs+, Mg2+, or guanylylimidodiphosphate. The specific irreversible binding was saturable, time- and temperature-dependent, and was linearly related to tissue mass. Several drugs were used to characterize this specific binding. Levorphanol was 1000 times more potent as an inhibitor than dextrorphan. mu Opioid ligands (sufentanil and morphine) were much better inhibitors than delta (ICI174,864) or kappa (U50,488H) ligands. The potency of [D-Ala2, D-Leu5]enkephalin (DADLE) was between those of sufentanil and ICI174,864. These results demonstrated that under appropriate conditions [3H]beta-FNA specifically and irreversibly bound to the mu opioid binding site. Membrane preparations labeled with [3H]beta-FNA in the presence or absence of 1 microM naloxone or beta-FNA were subjected to polyacrylamide gel electrophoresis under denaturing and reducing conditions. Fluorograms showed that [3H]beta-FNA specifically bound to a protein (most likely the mu opioid binding site) that migrated as a band with a molecular weight range of 68,000-97,000. Such electrophoretic behavior indicates that it is likely to be a glycoprotein. The glycoprotein nature was confirmed by its adsorption onto a wheat germ lectin-Sepharose column after solubilization and subsequent elution by N-acetyl-D-glucosamine. In this lectin column eluate, the mu opioid receptor was the only protein band labeled by [3H]beta-FNA in the total binding preparation, and no labeled protein was observed in the nonspecific binding preparation. When the wheat germ lectin column eluate of the total binding was treated with peptide:N-glycosidase F, the broad labeled band of Mr 68,000-97,000 became a sharp band of Mr 57,000 with high radioactivity and a faintly labeled band of Mr 49,000.
Mol Pharmacol 1987 Sep
PMID:Covalent labeling of mu opioid binding site by [3H]beta-funaltrexamine. 282 89

Monoclonal antibodies were raised against the surface of trypomastigote forms of Trypanosoma cruzi. Although some of these antibodies reacted against antigens shared by trypomastigote and epimastigote or amastigote forms, the majority were trypomastigote-specific. Trypomastigote-specific monoclonal antibodies recognized all infective stages, including trypomastigotes from the bloodstream of infected mice, insect feces, tissue culture and those resulting from differentiation of epimastigotes in axenic culture media. The monoclonal antibodies H1A10 and 6A2, as well as Fab fragments from H1A10, partially prevented T. cruzi invasion of LLC-MK2 cell monolayers (inhibition of 50-70%) when present throughout the entire experiment. Both antibodies recognized an 85 kDa glycoprotein (Tc-85) of the trypomastigote surface which contains N-acetyl-D-glucosamine and/or sialic acid.
Mol Biochem Parasitol 1986 Oct
PMID:Partial inhibition of trypomastigote entry into cultured mammalian cells by monoclonal antibodies against a surface glycoprotein of Trypanosoma cruzi. 353 65

The objectives of the present study were to identify and characterize biochemically the major antigens of Brugia malayi microfilariae, a filarial parasite that infects humans. IgG antibodies in sera of mice which had cleared parasites from the bloodstream reacted with 30, 55, 94 and 150 kDa molecules of living microfilariae radioiodinated by the Iodo-bead method. Sera of humans infected with the related filariae Wuchereria bancrofti, Loa loa or Onchocerca volvulus immunoprecipitated molecules of similar size as well as two additional proteins of 22 and 43 kDa. Sera of uninfected North Americans or mice infected with Trichinella spiralis or Schistosoma mansoni did not recognize these radioiodinated antigens. Experiments to examine the possible surface localization and metabolism of these antigens showed that they were removed from intact parasites exposed to chymotrypsin or trypsin and that immunogenic molecules of 30, 55, and 150 kDa were released into excretory-secretory products by viable microfilariae. [35S]Methionine biosynthetically labeled polypeptide antigens of 22, 30, 35 and 150 kDa were detected by antibody reacted with intact microfilariae and/or their excretion products. Antigens of 30, 55, and 150 kDa appear to be glycoproteins as they bound wheat germ agglutinin and were biosynthetically labeled with [14C]N-acetyl-D-glucosamine. These data suggest that the surface of B. malayi microfilariae is a dynamic structure which synthesizes and sheds antigens.
Mol Biochem Parasitol 1987 Jan 15
PMID:Immunochemical characterization and biosynthesis of major antigens of iodo-bead surface-labeled Brugia malayi microfilariae. 357 45


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