期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：35
页码：E8296-E8304
DOI：10.1073/pnas.1808284115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Thiol-based redox regulation is central to adjusting chloroplast functions under varying light conditions. A redox cascade via the ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) pathway has been well recognized to mediate the light-responsive reductive control of target proteins; however, the molecular basis for reoxidizing its targets in the dark remains unidentified. Here, we report a mechanism of oxidative thiol modulation in chloroplasts. We biochemically characterized a chloroplast stroma-localized atypical Trx from Arabidopsis , designated as Trx-like2 (TrxL2). TrxL2 had redox-active properties with an unusually less negative redox potential. By an affinity chromatography-based method, TrxL2 was shown to interact with a range of chloroplast redox-regulated proteins. The direct discrimination of thiol status indicated that TrxL2 can efficiently oxidize, but not reduce, these proteins. A notable exception was found in 2-Cys peroxiredoxin (2CP); TrxL2 was able to reduce 2CP with high efficiency. We achieved a complete in vitro reconstitution of the TrxL2/2CP redox cascade for oxidizing redox-regulated proteins and draining reducing power to hydrogen peroxide (H2O2). We further addressed the physiological relevance of this system by analyzing protein-oxidation dynamics. In Arabidopsis plants, a decreased level of 2CP led to the impairment of the reoxidation of redox-regulated proteins during light–dark transitions. A delayed response of protein reoxidation was concomitant with the prolonged accumulation of reducing power in TrxL2. These results suggest an in vivo function of the TrxL2/2CP redox cascade for driving oxidative thiol modulation in chloroplasts.
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