Physicochemical properties of amaranthin, the lectin from Amaranthus caudatus seeds

• Published in: Biochemistry (Easton) Vol. 29; no. 46; pp. 10555 - 10561
• Main Authors: Rinderle, Stephen J, Goldstein, Irwin J, Remsen, Edward E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.1990
• Subjects: amaranthin; AMARANTHUS CAUDATUS; Analytical, structural and metabolic biochemistry; Binding Sites; Biological and medical sciences; Carbohydrate Sequence; Cross-Linking Reagents; Disaccharides - chemical synthesis; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; GRAINE; Kinetics; LECTINA; LECTINE; Lectins - chemistry; Lectins - isolation & purification; Miscellaneous; Molecular Sequence Data; Molecular Weight; Naphthalenesulfonates; OLIGOSACARIDOS; OLIGOSACCHARIDE; physicochemical properties; Plant Lectins; PROPIEDADES FISICO-QUIMICAS; PROPRIETE PHYSICOCHIMIQUE; Proteins; Ribosome Inactivating Proteins; Ribosome Inactivating Proteins, Type 1; seeds; SEMILLA; Spectrometry, Fluorescence; Succinimides; Lectin; Seeds; Antibody; Molecular weight determination; Amaranthus caudatus; Crosslinking; Amaranthaceae; Sedimentation equilibrium; Binding capacity; Dicotyledones; Angiospermae; Distribution; Spermatophyta; Dialysis; Dimer; T antigen; Medical application; Physicochemical properties
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00498a019

Amaranthin is the lectin present in the seeds of Amaranthus caudatus, which specifically binds the T- disaccharide (Gal beta 1,3GalNAc alpha-O-). The lectin is composed of a single type of subunit with Mr = 33000-36000 (Rinderle et al., 1989). Equilibrium sedimentation (Mr = 62900) and low-angle laser light scattering (Mr = 61 400) methods have been used to unambiguously establish the native multimeric structure of amaranthin as a homodimer. These absolute molecular weight methods and the calculated Stokes radius (27.2 angstrom) indicate that the amaranthin dimer is highly compact relative to typical globular proteins, and thus, anomalous molecular weight values are obtained when simple size exclusion chromatography is used to determine the molecular weight of amaranthin. Studies with a homobifunctional cross-linking reagent and amaranthin further support the existence of a lectin homodimer. The stoichiometry of carbohydrate binding was determined to be one T-disaccharide-binding site per amaranthin subunit (Ka = 3.6 X 10(5) M-1). Amaranthin exhibits hydrophobic-binding properties as indicated by binding of 8-anilino-1-naphthalenesulfonate (Ka = 3.6 X 10(3) M-1) and 6-toluidinyl-2-naphthalenesulfonate (Ka = 2 X 10(4) M-1). Serological studies suggest that amaranthin does not appear to be present in the stems or leaves of the A. caudatus plant, nor were there any indications for the presence of cross-reactive material