Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02749 (beta2-glycoprotein I)
 836 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

C-reactive protein (CRP) is thought to play an important role in immunomodulation. The exact biologic function of this pentraxin protein is, however, still unclear. Here we report experiments designed to further characterize the binding properties of CRP. Using purified human CRP it could be shown that CRP immobilized onto polystyrene surfaces or onto latex beads binds distinct plasma glycoproteins including IgG, asialofetuin, asialo-beta 2-glycoprotein I and, likewise, synthetic glycoproteins as a lectin, exhibiting binding specificity for terminal galactosyl residues of the glycoprotein glycans. Binding of CRP to IgA, IgM, IgG, asialofetuin, asialo-beta 2-glycoprotein I and to synthetic glycoproteins requires immobilization onto surfaces of both CRP and the ligand. Fibronectin and fibrinogen are bound by surface-immobilized CRP also in soluble phase. Comparing various mono-, di-, and trisaccharides as competitive inhibitors of the lectin binding activity of CRP, only beta-D-Gal-(1-3)-D-GalNAc, beta-D-Gal-(1-4)-D-GalNAc, and beta-D-Gal-(1-4)-beta-D-Gal-(1-4)-D-GlcNAc had significant inhibitory power at a concentration of 8 mmol/liter. Binding activity of CRP was pH-dependent with an optimum at pH 5 to 6 and was reduced by 90% when pH was shifted from 6 to the physiologic pH value of 7.4. CRP exhibited lectin-like properties with binding specificity for galactosyl residues also when bound to K-562 erythroleukemia cells. It is therefore suggested that CRP immobilized onto surfaces exhibits lectin activity toward galactosyl groups preferentially in a mildly acidic environment as present at sites of inflammation.
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PMID:Lectin specificity and binding characteristics of human C-reactive protein. 162 92

By use of six highly purified exoglycosidases with well-defined specificity, the oligosaccharide units of human plasma beta 2-glycoprotein I (beta 2I) were modified by sequential enzymatic degradation. The released monosaccharides (NeuAc, Gal, GlcNAc, and Man) were quantified, and the carbohydrate compositions of the resulting glycoprotein (gp) derivatives were determined. The gp was found to be both partially sialylated and galactosylated. These findings which are in agreement with earlier reports suggest that the carbohydrate moiety of beta 2I possesses more bi- than tri-antennas, probably three of the former and two of the latter carbohydrate units. Circular dichroic (CD) spectra of native beta 2I and its derivatives were measured in aqueous buffer and 2-chloroethanol (2-CE). Analysis of these spectra for elements of secondary structure showed beta 2I and most of the derivatives to contain predominantly beta-sheet and beta-turn structures. The lack of alpha-helical structures in aqueous buffer was noted. Removal of a large portion of the carbohydrate moiety did not alter the CD spectra or secondary structure of beta 2I in either aqueous buffer or in 2-CE. However, after enzymatic removal of approximately 96% of the carbohydrate moiety, large significant changes in the spectra and secondary structures were observed. In aqueous buffer a shift in the wavelength minimum occurred, accompanied by an increase in the magnitude of the molar ellipticity and the amount of beta-turn, with a reduction in random coil. One-third of the amino acids which were originally in random coil conformation assumed beta-turns after removal of 96% of the carbohydrate moiety.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of the carbohydrate moiety on the secondary structure of beta 2-glycoprotein. I. Implications for the biosynthesis and folding of glycoproteins. 220 70

The amount and type of sialylation of tumor cell membranes depends on the activity of a number of different sialyltransferase enzymes. For the detection of specific activities in human colorectal carcinoma tissue several glycoprotein and glycolipid acceptors were used: desialylated fetuin, alpha 1-acid glycoprotein, beta 2-glycoprotein I, ovine submaxillaris mucin, and the gangliosides GM1, GM2, GM3 and GD1a. Because of their possible relevance for metastasis, precursors of Le(a) and Le(x) antigens, too, were employed, namely neoglycolipids produced by coupling LcOse4 or NeoLcOse4 oligosaccharides to L-alpha-phosphatidyl-ethanol-amine-dipalmitoyl. Our data indicate that human colorectal tumor tissue contains two highly active sialyltransferase enzymes, which are only weakly expressed in normal mucosa. These are a N-glycan-specific alpha 2,6-sialyltransferase, which was significantly increased in metastasizing tumors, and a Gal beta 1,3Gal-NAc-specific sialyltransferase, which was increased in tumors of early stages. A shift to enhanced alpha 2,6-sialylation of membrane glycoproteins during carcinogenesis was demonstrated by lectin ELISA analysis of magneto-bead separated tumor cells. Quantitative determination of specific sialyltransferase activities may be a sensitive tool for detection and monitoring of colon carcinoma.
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PMID:Different sialyltransferase activities in human colorectal carcinoma cells from surgical specimens detected by specific glycoprotein and glycolipid acceptors. 819