Abstract: Gibberellin-binding proteins were found on the membrane of young rice shoot. The dissociation constant (Kd) for GAs was approximately 6.5 × 10-8 mol/L, and the total concentration of the sites was 0. 3 pmol ·mg-1 protein. The binding activity of gibberellin-binding proteins was significantly affected by temperature and phi which was 140% higher at 0 ℃ than that at 25 ℃, and the optimal pH value was 5. Gibberellin-binding activity increased with the incubation time, reaching the maximum at 1 h. and then decreased gradually. Both IAA and ABA were able to compete with GA3 for gibberellin-binding proteins.

Key words: Rice: Gibberellin-binding protein, Binding characterization