Calcium-dependent regulation of photosynthesis in Chlamydomonas reinhardtii: Structural and functional dynamics of calredoxin, a chloroplast Ca2+-dependent thioredoxin

叶绿体Ca 2+运输（输入/输出），分配，传感和/或信号似乎是必不可少的叶绿体生物学，特别是有效的光合作用在绿色藻类和维管植物。有证据表明，存在一个调节网络，它感知叶绿体Ca 2+含量，参与光合作用的调节和蛋白质表达的控制。然而，这个网络的基本方面是未知的。在这里，我们将集中在钙氧还蛋白（CRX），一个新发现的因素在这个网络中，它作为一个钙依赖的硫氧还蛋白（TRX）在叶绿体。作为一种钙依赖性传感器-应答器，CRX将钙和氧化还原反应联系起来。Ca 2+结合CRX重塑其结构，允许结合和电子转移到叶绿体过氧化物酶（PRX 1），重要的光适应反应。我们的目标是（i）从机理上理解CRX和PRX 1之间的蛋白质-蛋白质相互作用。在这里，目标是了解Ca 2+驱动的结构变化如何允许CRX和PRX 1之间的结合和电子转移。我们进一步的目标（ii）解剖的互连CRX在Ca 2+和氧化还原依赖的监管网络，并了解其对叶绿体氧化还原平衡和光保护的影响。此外，我们的目标（iii）确定控制CRX表达的因素，从而可能扩大光感受和光合作用之间的联系，以及钙和氧化还原控制叶绿体。

Chloroplast Ca2+-transport (import/export), allocation, sensing and/or signaling appear to be essential for chloroplast biology and in particular for effective photosynthesis in green algae and vascular plants. There is evidence that a regulatory network exists which senses the chloroplast Ca2+ content, participates in regulation of photosynthesis and control of protein expression. Yet, basic aspects of this network are unknown. Herein we will focus on calredoxin (CRX), a newly identified factor in this network, which operates as a Ca2+-dependent thioredoxin (TRX) in the chloroplast. As a Ca2+-dependent sensor-responder, CRX links calcium and redox responses. Ca2+-binding to CRX remodels its structure allowing binding and electron transfer to chloroplast peroxiredoxin (PRX1), important for photo-acclimation responses. It is our aim (i) to mechanistically understand protein-protein interaction between CRX and PRX1. Here, the goal is to comprehend how the Ca2+-driven structural changes permit binding and electron transfer between CRX and PRX1. We further aim (ii) for dissecting the interconnection of CRX in the Ca2+- and redox-dependent regulatory networks and to understand its impact on chloroplast redox poise and photo-protection. Moreover, we aim (iii) to identify factors that control expression of CRX and thereby possibly expand the link between photoreception and photosynthesis as well as between calcium and redox control in chloroplasts.