Meyer Andreas J
Heidelberg Institute of Plant Sciences, University of Heidelberg, Heidelberg, Germany.
J Plant Physiol. 2008 Sep 8;165(13):1390-403. doi: 10.1016/j.jplph.2007.10.015. Epub 2008 Jan 2.
Formation of reactive oxygen species (ROS) is a common feature of abiotic and biotic stress reactions. ROS need to be detoxified to avoid deleterious reactions, but at the same time, the increased formation of ROS can also be exploited for redox signaling. Glutathione, as the most abundant low-molecular weight thiol in the cellular redox system, is used for both detoxification of ROS and transmission of redox signals. Detoxification of H(2)O(2) through the glutathione-ascorbate cycle leads to a transient change in the degree of oxidation of the cellular glutathione pool, and thus a change in the glutathione redox potential. The shift in the glutathione redox potential can be sensed by glutaredoxins (GRXs), small ubiquitous oxidoreductases, which reversibly transfer electrons between the glutathione redox buffer and thiol groups of target proteins. While very little is known about native GRX target proteins and their behavior in vivo, it is shown here that reduction-oxidation-sensitive GFP (roGFP), when expressed in plants, is an artificial target protein of GRXs. The specific interaction of roGFP with GRX results in continuous formation and release of the roGFP disulfide bridge depending on the actual redox potential of the cellular glutathione buffer. Ratiometric analysis of redox-dependent fluorescence allows dynamic imaging of the glutathione redox potential. It was hypothesized that a similar equilibration occurs between the glutathione buffer and native target proteins of GRXs. As a consequence, even minor deviations in the glutathione redox potential due to either depletion of reduced glutathione (GSH) or increasing oxidation can be exploited for fine tuning the activity of target proteins. The integration of the glutathione buffer with redox-active target proteins is a local reaction in specific subcellular compartments. This observation emphasizes the importance of subcellular compartmentalization in understanding the biology of the cellular redox system in plants.
活性氧（ROS）的形成是生物和非生物胁迫反应的一个共同特征。ROS需要被解毒以避免有害反应，但同时，ROS生成的增加也可用于氧化还原信号传导。谷胱甘肽作为细胞氧化还原系统中最丰富的低分子量硫醇，既用于ROS解毒，也用于氧化还原信号的传递。通过谷胱甘肽-抗坏血酸循环对H₂O₂进行解毒会导致细胞谷胱甘肽池氧化程度的瞬时变化，从而使谷胱甘肽氧化还原电位发生变化。谷胱甘肽氧化还原电位的变化可被谷氧还蛋白（GRXs）感知，谷氧还蛋白是一类广泛存在的小氧化还原酶，可在谷胱甘肽氧化还原缓冲液和靶蛋白的硫醇基团之间可逆地转移电子。虽然对天然GRX靶蛋白及其体内行为了解甚少，但本文表明，还原-氧化敏感型绿色荧光蛋白（roGFP）在植物中表达时是GRXs的人工靶蛋白。roGFP与GRX的特异性相互作用导致roGFP二硫键根据细胞谷胱甘肽缓冲液的实际氧化还原电位持续形成和释放。基于氧化还原的荧光比率分析可对谷胱甘肽氧化还原电位进行动态成像。据推测，在谷胱甘肽缓冲液和GRXs的天然靶蛋白之间也会发生类似的平衡。因此，即使由于还原型谷胱甘肽（GSH）的消耗或氧化增加导致谷胱甘肽氧化还原电位出现微小偏差，也可用于微调靶蛋白的活性。谷胱甘肽缓冲液与氧化还原活性靶蛋白的整合是特定亚细胞区室中的局部反应。这一观察结果强调了亚细胞区室化在理解植物细胞氧化还原系统生物学中的重要性。
