Abstract：
Protochlorophyllide oxidoreductase (POR), which converts protochlorophyllide into chlorophyllide, is the only light-dependent enzyme in chlorophyll biosynthesis. While its catalytic reaction and importance for chloroplast development are well understood, little is known about the post-translational control of PORs. Here, we show that cpSRP43 and cpSRP54, two components of the chloroplast signal recognition particle pathway, play distinct roles in optimizing the function of PORB, the predominant POR isoform in Arabidopsis. The chaperone cpSRP43 stabilizes the enzyme and provides appropriate amounts of PORB during leaf greening and heat shock, whereas cpSRP54 enhances its binding to the thylakoid membrane, thereby ensuring adequate levels of metabolic flux in late chlorophyll biosynthesis. Furthermore, cpSRP43 and the DnaJ-like protein CHAPERONE-LIKE PROTEIN of POR1 concurrently act to stabilize PORB. Overall, these findings enhance our understanding of the coordinating role of cpSPR43 and cpSRP54 in the post-translational control of chlorophyll synthesis and assembly of photosynthetic chlorophyll-binding proteins.
摘要：
原叶绿素氧化还原酶(POR),将原叶绿素转化为叶绿素，是叶绿素生物合成中唯一的光依赖性酶。虽然它的催化反应和对叶绿体发育的重要性是众所周知的，对PORs的翻译后控制知之甚少。这里,我们发现cpSRP43和cpSRP54是叶绿体信号识别粒子通路的两个组成部分,在优化PORB的功能方面发挥着不同的作用，拟南芥中主要的POR亚型。伴侣cpSRP43稳定酶，并在叶片变绿和热休克期间提供适量的PORB，而cpSRP54增强了它与类囊体膜的结合，从而确保晚期叶绿素生物合成中足够水平的代谢通量。此外，cpSRP43和POR1的DnaJ样蛋白质链环蛋白样蛋白同时起稳定PORB的作用。总的来说,这些发现增强了我们对cpSPR43和cpSRP54在叶绿素合成和光合叶绿素结合蛋白组装的翻译后控制中的协调作用的理解.
