非洲爪猿卵母细胞代表了用于表征膜转运蛋白特性的最通用的模型系统之一。然而,用于研究质子耦合的反载体,迄今为止,非洲爪猿卵母细胞的使用仅限于所谓的基于注射的转运试验.在这样的检测中,将化合物直接注射到卵母细胞的细胞质中,并通过监测底物流出来检测转运,对内部扩散和浓度控制不佳与机械表征不相容。在这项研究中,我们提出了一个反向pH梯度转运试验。在这里,面向外的质子梯度能够通过容易的基于进口的转运测定来表征质子反转运蛋白。我们描述了两种在卵母细胞膜上建立持续的面向外的质子梯度的方法,即通过施加碱性外部条件或通过令人惊讶地稳定的羰基氰化物间氯苯基腙(CCCP)介导的胞质溶胶酸化。以前,遗传证据表明,拟南芥的DTX18对于叶片表面上羟基肉桂酸酰胺对香豆素(香豆素)防御化合物的沉积至关重要。然而,尚未提供其运输香豆酚-胍丁胺能力的直接证据。这里,使用非洲爪的卵母细胞作为表达宿主,我们证明了DTX18通过基于注射和反向pH梯度转运试验转运香豆酰基-胍丁胺的能力。值得注意的是,通过显示DTX18能够针对其浓度梯度积累其底物,我们展示了后者与机械调查的兼容性。
Xenopus oocytes represent one of the most versatile model systems for characterizing the properties of membrane transporters. However, for studying proton-coupled antiporters, the use of Xenopus oocytes has so far been limited to so-called injection-based transport assays. In such assays, where the compound is injected directly into the oocytes\' cytosol and transport is detected by monitoring substrate efflux, poor control over internal diffusion and concentration are incompatible with mechanistic characterizations. In this study, we present an inverse pH-gradient transport assay. Herein, an outward-facing proton gradient enables the characterization of proton antiporters via facile import-based transport assays. We describe two approaches for establishing sustained outward-facing proton gradients across the oocyte membrane, namely by applying alkaline external conditions or through surprisingly stable carbonyl cyanide m-chlorophenyl-hydrazone (CCCP)-mediated acidification of the cytosol. Previously, genetic evidence has shown that DTX18 from Arabidopsis thaliana is essential for the deposition of the hydroxycinnamic acid amide p-coumaroylagmatine (coumaroylagmatine) defence compound on the leaf surface. However, direct evidence for its ability to transport coumarol-agmatine has not been provided. Here, using Xenopus oocytes as expression hosts, we demonstrate DTX18\'s ability to transport coumaroyl-agmatine via both injection-based and inverse pH-gradient transport assays. Notably, by showing that DTX18 is capable of accumulating its substrate against its concentration gradient, we showcase the compatibility of the latter with mechanistic investigations.