title: Binding site for chitin oligosaccharides in the soybean plasma membrane.
abstract: Affinity cross-linking of the plasma membrane fraction to an (125)I-labeled chitin oligosaccharide led to the identification and characterization of an 85-kD, chitin binding protein in plasma membrane-enriched fractions from both suspension-cultured soybean cells and root tissue. Inhibition analysis indicated a binding preference for larger (i.e. degrees of polymerization = 8) N-acetylated chitin molecules with a 50% inhibition of initial activity value of approximately 50 nM. N-Acetyl-glucosamine and chitobiose showed no inhibitory effects at concentrations as high as 250 microM. It is noteworthy that the major lipo-chitin oligosaccharide Nod signal produced by Bradyrhizobium japonicum was also shown to be a competitive inhibitor of ligand binding. However, the binding site appeared to recognize the chitin portion of the Nod signal, and it is unlikely that this binding activity represents a specific Nod signal receptor. Chitooligosaccharide specificity for induction of medium alkalinization and the generation of reactive oxygen in suspension-cultured cells paralleled the binding activity. Taken together, the presence of the chitin binding protein in the plasma membrane fraction and the specificity and induction of a biological response upon ligand binding suggest a role for the protein as an initial response mechanism for chitin perception in soybean (Glycine max).
authors.affiliation: Department of Microbiology, University of Tennessee, M409 Walters Life Science Building, Knoxville, Tennessee 37996-0845, USA.
authors.forename: R B
authors.initials: RB
authors.lastname: Day
authors.forename: M
authors.initials: M
authors.lastname: Okada
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.forename: K
authors.initials: K
authors.lastname: Tsukada
authors.forename: H
authors.initials: H
authors.lastname: Zaghouani
authors.forename: N
authors.initials: N
authors.lastname: Shibuya
authors.forename: G
authors.initials: G
authors.lastname: Stacey
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002686:Chitin / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D015398:Signal Transduction; D013025:Glycine max / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; D008565:Membrane Proteins; D002686:Chitin; C091899:Nod factor V, Bradyrhizobium japonicum