title: Abscisic acid-specific binding sites in the flesh of developing apple fruit.
abstract: Abscisic acid (ABA) specific-binding sites localized in the cytosol were identified and characterized in the flesh of developing apple (Malus pumila L. cv. Starkrimon) fruit. ABA binding activity was scarcely detectable in the microsomes but high ABA binding activity in the cytosolic fraction was detected. The ABA-binding sites possessed a protein nature with both active serine residues and thiol-groups of cysteine residues in their functional binding sites. ABA binding was shown to be saturable, reversible and of high affinity. A Scatchard plot provided evidence for two different ABA binding proteins, one with higher affinity (K(d)=2.3 nM) and the other with lower affinity (K(d)=58.8 nM). Phaseic acid, trans-ABA and (-)-ABA had essentially no affinity for the binding proteins, indicating their stereo-specificity to bind physiologically active cis-(+)-ABA. The time-course, pH- and temperature-dependence of the ABA-binding proteins were determined. It is hypothesized that the detected ABA-binding proteins may be putative ABA-receptors that mediate ABA signals during fruit development.
authors.affiliation: Laboratory of Molecular Developmental Biology of Fruit Trees, Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100094, PR China. zhangdp@public2.east.cn.net
authors.forename: D P
authors.initials: DP
authors.lastname: Zhang
authors.forename: S W
authors.initials: SW
authors.lastname: Chen
authors.forename: Y B
authors.initials: YB
authors.lastname: Peng
authors.forename: Y Y
authors.initials: YY
authors.lastname: Shen
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D005638:Fruit / Q000254:growth & development / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D027845:Malus / Q000254:growth & development* / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D013696:Temperature; D013997:Time Factors
chemical_list: D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D000040:Abscisic Acid