Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
School of Life Science and Technology, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
Proc Natl Acad Sci U S A. 2021 Dec 21;118(51). doi: 10.1073/pnas.2114952118.
Thioredoxin (Trx) is a protein that mediates the reducing power transfer from the photosynthetic electron transport system to target enzymes in chloroplasts and regulates their activities. Redox regulation governed by Trx is a system that is central to the adaptation of various chloroplast functions to the ever-changing light environment. However, the factors involved in the opposite reaction (i.e., the oxidation of various enzymes) have yet to be revealed. Recently, it has been suggested that Trx and Trx-like proteins could oxidize Trx-targeted proteins in vitro. To elucidate the in vivo function of these proteins as oxidation factors, we generated mutant plant lines deficient in Trx or Trx-like proteins and studied how the proteins are involved in oxidative regulation in chloroplasts. We found that -type Trx and two types of Trx-like proteins, Trx-like 2 and atypical Cys His-rich Trx (ACHT), seemed to serve as oxidation factors for Trx-targeted proteins, such as fructose-1,6-bisphosphatase, Rubisco activase, and the γ-subunit of ATP synthase. In addition, ACHT was found to be involved in regulating nonphotochemical quenching, which is the mechanism underlying the thermal dissipation of excess light energy. Overall, these results indicate that Trx and Trx-like proteins regulate chloroplast functions in concert by controlling the redox state of various photosynthesis-related proteins in vivo.
硫氧还蛋白（Trx）是一种介导光合电子传递系统将还原力传递到叶绿体靶酶并调节其活性的蛋白质。Trx 调控的氧化还原调节是一个核心系统，对于各种叶绿体功能适应不断变化的光照环境至关重要。然而，参与相反反应（即各种酶的氧化）的因素尚未被揭示。最近，有人提出 Trx 和 Trx 样蛋白可以在体外氧化 Trx 靶向蛋白。为了阐明这些蛋白作为氧化因子的体内功能，我们生成了 Trx 或 Trx 样蛋白缺陷的突变体植物系，并研究了这些蛋白如何参与叶绿体中的氧化调节。我们发现 -型 Trx 和两种 Trx 样蛋白（Trx-like 2 和非典型 Cys His-rich Trx（ACHT））似乎作为 Trx 靶向蛋白（如果糖-1,6-二磷酸酶、Rubisco 激活酶和 ATP 合酶的 γ 亚基）的氧化因子。此外，还发现 ACHT 参与调节非光化学猝灭，这是过量光能热耗散的机制。总的来说，这些结果表明 Trx 和 Trx 样蛋白通过控制体内各种光合作用相关蛋白的氧化还原状态协同调节叶绿体功能。
