Sandoz Crop Protection Corporation, 975 California Avenue, Palo Alto, California 94304-1104.
Plant Physiol. 1992 Jan;98(1):101-7. doi: 10.1104/pp.98.1.101.
We have described the inhibition of polar auxin transport by several phytotropins including 1-N-naphthylphthalamic acid (NPA) and quercetin. Semicarbazones (substituted phenylsemicarbazones of 2-acetylarylcarboxylic acids) are inhibitors consistent with previously predicted general structural requirements for auxin transport inhibitors. The best semicarbazone derivative tested to date, hereafter called SCB-I, binds to the NPA binding protein with high affinity, K(b) = 4 nanomolar. Quantification of the binding of various phytotropins allows us to make some general statements concerning the structure/properties of the NPA binding protein. The data suggest that the ligand binding region of this protein is multifaceted, a conclusion supported by the chemical predictions of Katekar and Geissler ([1977] Plant Physiol 60: 826-829). Although the data do not allow us to make specific conclusions on the structure of the binding site, they do show that both NPA and SCB-I could each occupy two regions of the protein. At least one of these binding regions appears to be common for both inhibitors of auxin transport. We suggest that the diversity of the binding site structure reflects the possible existence of more than one type of natural ligand controlling the process of auxin transport.
我们已经描述了几种植物生长调节剂对极性生长素运输的抑制作用，包括 1-N-萘基邻苯二甲酰胺（NPA）和槲皮素。半卡巴嗪（2-乙酰芳基羧酸的取代苯半卡巴嗪）是与先前预测的生长素运输抑制剂的一般结构要求一致的抑制剂。迄今为止测试的最佳半卡巴嗪衍生物，以下称为 SCB-I，与 NPA 结合蛋白具有高亲和力结合，K(b) = 4 纳摩尔。各种植物生长调节剂结合的定量分析使我们能够就 NPA 结合蛋白的结构/性质做出一些一般性陈述。这些数据表明，该蛋白的配体结合区域是多方面的，这一结论得到了 Katekar 和 Geissler（[1977]植物生理学 60:826-829）的化学预测的支持。尽管数据不允许我们对结合位点的结构做出具体结论，但它们确实表明 NPA 和 SCB-I 都可以占据蛋白的两个区域。至少有一个结合区域似乎对两种生长素运输抑制剂都是通用的。我们认为结合位点结构的多样性反映了可能存在不止一种类型的天然配体来控制生长素运输过程。
