Fluorescence analysis of hormone binding activities of wheat germ agglutinin

✍ Scribed by Vanya P. Bogoeva; Maya A. Radeva; Lyubomira Y. Atanasova; Stoyanka R. Stoitsova; Raina N. Boteva

• Book ID: 104003280
• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 197 KB
• Volume: 1698
• Category: Article
• ISSN: 1570-9639
• DOI: 10.1016/j.bbapap.2003.12.002

✦ Synopsis

Wheat germ agglutinin (WGA) from embryos of the monocotyledonous plant Triticum vulgaris (Graminaceae) is a carbohydrate binding protein characterized by high specificity to N-acetyl-D-glucosamine and N-acetyl-D-neuraminic acid. In this study we show that parallel to its carbohydrate binding activities, WGA binds with several orders of magnitude higher affinity adenine, adenine-related cytokinins: kinetin, zeatin and isopentenyl-adenine as well as abscisic and gibberellic acids (K d 0.43 -0.65 AM). Its interactions with these ligands cause conformational rearrangements in the protein molecules and significant enhancement of the protein tryptophan fluorescence (up to 60%) allowing characterization of the protein -hormone complexes. Dimeric WGA molecules possess two different classes of binding sites for the fluorescent hydrophobic probe 2-( p-toluidinyl) naphthalene sulfonic acid (TNS) as suggested by the sigmoid shape of the fluorescence titration curve and the value of the Hill coefficient (n H 1.6 F 0.3). The plant hormones displace part of the bound TNS probe and share the higher affinity TNS binding sites. These results characterize WGA as a hormone-binding protein.