Affiliation:
1. Laboratory of Molecular Developmental Biology of Fruit Trees, China National Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, 100094 Beijing, Peoples Republic of China
Abstract
Abstract
Purification of abscisic acid (ABA)-binding proteins is considered to constitute a major step toward isolating ABA receptors. We report here that an ABA-binding protein was for the first time, to our knowledge, purified from the epidermis of broad bean (Vicia faba) leaves via affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing electrophoresis, and isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis two-dimensional electrophoresis of the purified ABA-binding protein all identified a single protein band with a molecular mass of 42 kD and an isoelectric point 4.86. The Scatchard plot for the purified protein showed a linear function with a maximum binding activity of 0.87 mol mol−1protein and an equilibrium dissociation constant of 21 nm, indicating that the purified protein may be a monomeric one, possessing one binding site. The ABA-binding protein was enriched more than 300-fold with a yield of 14%. (−)ABA and trans-ABA were substantially incapable of displacing 3H-(±)ABA bound to the ABA-binding protein, and (±)ABA was less effective than (+)ABA in the competition. These findings allow establishment of the stereospecificity of the 42-kD protein and suggest its ABA receptor nature. Pretreatment of the guard cell protoplasts of broad bean leaves with the monoclonal antibody raised against the 42-kD protein significantly decreased the ABA specific-induced phospholipase D activity in a dose-dependent manner. This physiological significance provides more clear evidence for the potential ABA-receptor nature of the 42-kD protein.
Publisher
Oxford University Press (OUP)
Subject
Plant Science,Genetics,Physiology
Cited by
106 articles.
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