Lectins are ubiquitous proteins of nonimmune origin, present in plants, microorganisms, animals and humans which specifically bind defined monosugars or oligosaccharide structures. Great progress has been made in recent years in understanding crucial roles played by lectins in many biological processes. Elucidation of carbohydrate specificity of human and animal lectins is of great importance for better understanding of these processes. Long before the role of carbohydrate-protein interactions had been explored, many lectins, mostly of plant origin, were identified, characterized and applied as useful tools in studying glycoconjugates. This review focuses on the specificity-based lectin classification and the methods of measuring lectin-carbohydrate interactions, which are used for determination of lectin specificity or for identification and characterization of glycoconjugates with lectins of known specificity. The most frequently used quantitative methods are shortly reviewed and the methods elaborated and used in our laboratories, based on biotinylated lectins, are described. These include the microtiter plate enzyme-linked lectinosorbent assay, lectinoblotting and lectin-glycosphingolipid interaction on thin-layer plates. Some chemical modifications of lectin ligands on the microtiter plates and blots (desialylation, Smith degradation, beta-elimination), which extend the applicability of these methods, are also described.
It is well documented that serum IgG from rheumatoid arthritis (RA) patients exhibits decreased galactosylation of its conservative N-glycans (Asn-297) in CH2 domains of the heavy chains; it has been shown that this agalactosylation is proportional to disease severity. In the present investigation we analyzed galactosylation of IgG derived from the patients using a modified ELISA-plate test, biosensor BIAcore and total sugar analysis (GC-MS). For ELISA and BIAcore the binding of IgG preparations, purified from the patients' sera, to two lectins: Ricinus communis (RCA-I) and Griffonia simplicifolia (GSL-II) was applied. Based on ELISA-plate test an agalactosylation factor (AF, a relative ratio of GSL-II/RCA-I binding) was calculated, which was proportional to actual disease severity. Repeated testing of several patients before and after treatment with methotrexate (MTX) alone or in combination with Remicade (a chimeric antibody anti-TNF-alpha) supplied results indicating an increase of IgG galactosylation during the treatment. This introductory observation suggests that IgG galactosylation may be an additional indicator of the RA patients' improvement.
Background: Inheritable NOR polyagglutination is a rare phenomenon caused by the unusual Gal(␣1-4)GalNAc glycolipid epitope. Results: A point mutation, 631 CϾG, in the gene encoding Gb3/CD77 synthase causes the enzyme to synthesize both Gal(␣1-4)Gal-and Gal(␣1-4) GalNAc-moieties.
Conclusion:The results pinpoint the cause of the NOR phenotype. Significance: This is the first report of an altered acceptor specificity of a glycosyltransferase caused by a point mutation.
NOR is a rare inheritable polyagglutination phenomenon that has been described in two families. Our recent studies on these erythrocytes showed they contained at least two unique neutral glycosphingolipids, and based on their reactivity with Griffonia simplicifolia IB4 (GSL-IB4) isolectin (Kusnierz-Alejska, G., Duk, M., Storry, J. R., Reid, M. E., Wiecek, B., Seyfried, H., and Lisowska, E. (1999) Transfusion 39, 32-38), both oligosaccharide chains terminated with an ␣-galactose residue. The reactivity with GSL-IB4 suggested that these oligosaccharide chains terminated with a Gal␣133Gal-sequence and that anti-NOR agglutinins were common human anti-Gal␣133Gal xenoantibodies. In this report we describe the structure of one NOR component (NOR1) that migrated on thinlayer chromatographic plates in the region of pentaglycosylceramides. Treatment of this sample with ␣-galactosidase and -N-acetylhexosaminidase was followed by highperformance thin-layer chromatography with product detection by lectins and the anti-Gb 4 monoclonal antibody. The results suggested that NOR1 was an ␣-galactosylated Gb 4 Cer with a -N-acetylhexosaminidase-resistant GalNAc residue. Gas phase disassembly by ion trap mass spectrometry analysis showed the sequence to be Hex134HexN133Hex134Hex134Hex linked to a ceramide composed of C 18 sphingosine and a C 24 monounsaturated fatty acid. Together these data indicate NOR1 to be a novel Gal␣134GalNAc133Gal␣134Gal134 Glc-Cer structure. Additionally it has been shown that NOR glycolipids are recognized by human antibodies that were distinct from the known anti-Gal␣133Gal xenoantibodies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.