Jean-Paul Privat

Bio: Jean-Paul Privat is an academic researcher from University of Orléans. The author has contributed to research in topics: Wheat germ agglutinin & Tryptophan. The author has an hindex of 10, co-authored 14 publications receiving 464 citations.

Fluorescence Studies of Saccharide Binding to Wheat-Germ Agglutinin (Lectin)

Abstract: Wheat germ agglutinin was isolated in pure form by a method adapted from D. LeVine, M. J. Kaplan and P. J. Greenaway, Biochem. J. 129, 847–856 (1972). Amino-acid composition calculated for a molecular weight of 23 500 showed that the protein contained four tryptophan residues and was rich in half-cystine (38 residues) and glycine (51 residues). Analysis of the fluorescence spectrum showed a characteristic tryptophan emission with a maximum centered at 348 nm. The spectrum is almost the same between pH 3.5 and 9.0. By adding N-acetylglucosaminides (β-d-GlcNAc 1 4)n-d-GlcNAc, an enhancement of the fluorescence intensity was detected. Moreover, binding of the dimer and higher GlcNAc oligomers induced a 10-nm shift of the emission maximum towards shorter wavelengths indicating that the environment of one or several tryptophan residues was altered by addition of ligands. The pH dependence of the fluorescence quantum yields shows that the tryptophan fluorescence is not altered by any ionisable group which possesses a pK in the range 4.0–9.0 in both the free and the complexed protein. Association constants were determined by measuring the change in fluorescence intensity produced by addition of different glucosaminides. These constants increased with chain length up to the trimer. No cooperative effect could be found with any ligand. It was shown that the carbohydrate binding is abolished below pH 2.8 and that a protein carboxyl group of pKa= 3.9 is involved. Our results are discussed and compared with the model proposed by A. K. Allen, A. Neuberger and N. Sharon, Biochem. J. 131, 155–162 (1973).

The lectins : carbohydrate-binding proteins of plants and animals

Abstract: Publisher Summary Lectins play an important role in the development of immunology. Lectins also find application in serological laboratories for typing blood and determining secretor status, separating leucocytes from erythrocytes, and agglutinating cells from blood in the preparation of plasma. They serve as reagents for the detection, isolation, and characterization of carbohydrate-containing macromolecules, including blood-group antigens. In their interaction with saccharides, lectins serve as models for carbohydrate-specific antibodies, with the important advantage to purify lectins in gram quantities. Lectins are classified according to their carbohydrate-binding specificity that includes D-mannose(D-glucose)-binding lectins and 2-acetamido-2-deoxy-D-glucose-binding lectins. The chapter considers only those lectins that have been purified to homogeneity, and studied with regard to their biophysical, biochemical, and carbohydrate-binding specificity. The chapter also describes the cell-binding and biological properties of lectins. The chapter concludes with the description of several glycopeptide structures showing the carbohydrate-binding loci with which various lectins interact.

Two LysM receptor molecules, CEBiP and OsCERK1, cooperatively regulate chitin elicitor signaling in rice

Abstract: Chitin is a major molecular pattern for various fungi, and its fragments, chitin oligosaccharides, are known to induce various defense responses in plant cells. A plasma membrane glycoprotein, CEBiP (chitin elicitor binding protein) and a receptor kinase, CERK1 (chitin elicitor receptor kinase) (also known as LysM-RLK1), were identified as critical components for chitin signaling in rice and Arabidopsis, respectively. However, it is not known whether each plant species requires both of these two types of molecules for chitin signaling, nor the relationships between these molecules in membrane signaling. We report here that rice cells require a LysM receptor-like kinase, OsCERK1, in addition to CEBiP, for chitin signaling. Knockdown of OsCERK1 resulted in marked suppression of the defense responses induced by chitin oligosaccharides, indicating that OsCERK1 is essential for chitin signaling in rice. The results of a yeast two-hybrid assay indicated that both CEBiP and OsCERK1 have the potential to form hetero- or homo-oligomers. Immunoprecipitation using a membrane preparation from rice cells treated with chitin oligosaccharides suggested the ligand-induced formation of a receptor complex containing both CEBiP and OsCERK1. Blue native PAGE and chemical cross-linking experiments also suggested that a major portion of CEBiP exists as homo-oligomers even in the absence of chitin oligosaccharides.