期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：5
页码：1515-1519
DOI：10.1073/pnas.79.5.1515
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A rapid method for assaying [3H]gibberellin A4 bound to a soluble protein from cucumber hypocotyls by using DEAE-cellulose filter discs is described. The binding is saturable, reversible with unlabeled gibberellin A4, and has a half-life of association under nonequilibrium conditions at 0-4{degrees}C of 6-7 min. By using this assay, the dissociation constant (Kd) was estimated to be 70 nM and the number of binding sites, 0.4 pmol mg-1 of soluble protein or 0.69 pmol g-1 (fresh weight) of hypocotyls. The speed and reliability of the assay make it invaluable for kinetic studies involving competitors. Thus, it has been possible to show that gibberellins that are biologically active in a cucumber bioassay compete for binding to the same protein and their calculated affinity constants bear a direct relationship to their known activities in the cucumber bioassay. Gibberellins that are inactive in this bioassay and other plant hormones, such as indoleacetic acid, abscisic acid, and kinetin, show a noncompetitive interaction.
