Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycophorin A, the major human erythrocyte sialoglycoprotein, contains a significant amount of phosphorus when isolated by the lithium diiodosalicylate-phenol procedure. Only a small percentage (approximately 1%) of this phosphorus is phosphoprotein. 31P nuclear magnetic resonance (NMR) analysis of glycophorin A has identified the remaining phosphorus content as phospholipid in origin. From the 31P chemical shifts, the phospholipid has been identified as diphosphoinositide. 31P NMR spectra of the peptides produced by trypsin hydrolysis of glycophorin A reveal that all the diphosphoinositide is closely associated with the hydrophobic region of the protein, suggesting that there is a specific affinity between this phospholipid and the intramembranous portion of glycophorin A.
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PMID:31P nuclear magnetic resonance evidence for polyphosphoinositide associated with the hydrophobic segment of glycophorin A. 19 Oct 66

Glycophorin A, a major glycoprotein of the red blood cell, is reconstituted in small lipid vesicles (250-300 A in diameter) by using cholate detergent solubilization followed by rapid removal of cholate on a molecular sieve column. The extent of glycophorin incorporation is found to be critically dependent on the amount of cholate used, with higher amounts yielding vesicles with higher percentages of glycophorin. Vesicles with as much as 1 molecule of protein per 20 molecules of lipid can be prepared. Data on the vesicles obtained by using hydrolytic enzymes such as neuraminidase and trypsin, combined with amino acid analysis, suggest that glycophorin is incorporated in a transbilayer fashion with a high fraction of the molecules oriented with the carbohydrate-containing amino terminus to the vesicle exterior. Interaction of the protein with the hydrophobic portion of the bilayer is apparent in proton nuclear magnetic resonance spectra, and lipid line-width increases have been used to characterize the strength and stoichiometry of interaction. Glycophorin is found to affect directly as many as 40 lipid molecules per molecule of protein; however, the magnitude of the effects is not large.
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PMID:Small unilamellar vesicles containing glycophorin A. Chemical characterization and proton nuclear magnetic resonance studies. 626 87

Plasmodium falciparum merozoites recognize and attach to glycophorins, the surface sialoglycoproteins of human erythrocytes. The structural requirements for a merozoite binding site were studied with the use of two methods. In the first, certain glycophorins and their tryptic fragments were added directly to isolated merozoites prior to their addition to erythrocytes. Low concentrations (50 micrograms ml-1) of glycophorin A inhibited merozoite invasion. At higher concentrations a mixture of glycophorins A, B and C (GPS) (100 micrograms ml-1) and glycophorin B (200 micrograms ml-1) also inhibited invasion. GPS from Tn erythrocytes which lack both sialic acid and galactose residues was almost as effective as normal GPS in blocking invasion. None of the monosaccharides present on glycophorin, including N-acetylneuraminic acid, inhibited merozoite invasion. Erythrocytes treated with lectins were only partially resistant to invasion. These results indicated that the oligosaccharide side chains are not the major structural determinant of the merozoite binding site. Glycophorin A was cleaved by trypsin and the separated fragments added to merozoites. Only the external N-terminal tryptic fragment T1 and the trypsin resistant hydrophobic core, T6, showed some, but considerably less, inhibitory activity than the intact molecule. In the second approach, the binding of 125I-labeled GPS to isolated merozoites was determined. 125I-GPS binding was saturated at 0.23 micrograms for 10(9) merozoites and was competitively inhibited by unlabeled GPS but not by free sugars. Desialylated GPS bound almost to the same extent as the intact molecule.
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PMID:Binding of glycophorins to Plasmodium falciparum merozoites. 636 23

Glycophorin A (GPA), the major sialoglycoprotein of human red cells, bears blood group MN determinants, and is a useful marker of the erythroid lineage in differentiating cells. Five monoclonal antibodies that react with GPA and possess a spectrum of serologic properties and fine specificities were obtained by immunization of mice with umbilical cord erythrocytes. Three antibodies, B22A, D22 and E11B, did not agglutinate En(a-) erythrocytes, genetic variants that lack GPA, and F11 and J11A agglutinated these cells very weakly. Antibodies B22A, E11B, and F11 agglutinated protease-treated cells more strongly than untreated erythrocytes, and they appeared to react with a peptide determinant located on the C-terminal side of the site at which trypsin cleaves GPA in the intact erythrocyte. In contrast to B22A and E11B, the hemagglutinating activity of F11 was not inhibited by purified GPA, nor did it bind to GPA in a solid phase immunoassay, but it immunoprecipitated GPA. Antibodies D22 and J11A appeared to be directed against carbohydrate determinants, or conformational determinants created by hydrogen bonding or electrostatic interactions between carbohydrate and protein. A preferential reaction of antibody J11A with MM over NN GPA was demonstrated by its reactions with enzyme-treated erythrocytes, its inhibition by purified GPA or its tryptic fragments, and by an ELISA assay.
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PMID:Diverse specificities of five monoclonal antibodies reactive with glycophorin A of human erythrocytes. 686 32

Invasion of erythrocytes by Plasmodium merozoites is an intricate process involving multiple receptor-ligand interactions. The glycophorins and an unknown trypsin sensitive factor are all erythrocyte receptors used during invasion by the major human pathogen Plasmodium falciparum. However, only one erythrocyte receptor, Glycophorin A, has a well-established cognate parasite ligand, the merozoite protein erythrocyte binding antigen-175 (EBA-175). The involvement of several other parasite proteins during invasion have been proposed, but no direct evidence links them with a specific invasion pathway. Here we report the identification and characterization of P. falciparum normocyte binding protein 1 (PfNBP1), an ortholog of Plasmodium vivax reticulocyte binding protein-1. PfNBP1 binds to a sialic acid dependent trypsin-resistant receptor on the erythrocyte surface that appears to be distinct from known invasion receptors. Antibodies against PfNBP1 can inhibit invasion of trypsinized erythrocytes and two P. falciparum strains that express truncated PfNBP1 are unable to invade trypsinized erythrocytes. One of these strain, 7G8, also does not invade Glycophorin B-negative erythrocytes. PfNBP1 therefore defines a novel trypsin-resistant invasion pathway and adds a level of complexity to current models for P. falciparum erythrocyte invasion.
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PMID:A Plasmodium falciparum homologue of Plasmodium vivax reticulocyte binding protein (PvRBP1) defines a trypsin-resistant erythrocyte invasion pathway. 1173 72