叶绿体硫氧还蛋白系统的调节机制

硫氧还蛋白(Trx)属于巯基-二硫键氧化还原酶家族, 通过作用于底物蛋白侧链2个半胱氨酸残基之间的二硫键(还原、异构和转移)来调控胞内蛋白的结构和功能。叶绿体Trx系统包括Trx及Trx类似蛋白、铁氧还蛋白(Fd)依赖的硫氧还蛋白还原酶(FTR)和还原型烟酰腺嘌呤二核苷磷酸(NADPH)依赖的硫氧还蛋白还原酶C (NTRC)。除了基质蛋白酶类活性变化及叶绿体蛋白的转运受Trx系统调控之外, 在叶绿体中还存在1条跨类囊体膜的还原势传递途径, 把基质Trx的还原势经跨膜转运蛋白介导, 最终传递给类囊体腔蛋白。FTR和NTRC共同作用维持叶绿体的氧化还原平衡。该文对叶绿体硫氧还蛋白系统的调节机制进行了综述, 同时讨论了叶绿体硫氧还蛋白系统对维持植物光合效率的重要意义。

Regulatory Mechanism of Thioredoxin (Trx) in Chloroplasts

Thioredoxins (Trx), a family of thiol-disulfide oxidoreductases, function as protein disulfide reductases to disulfide isomerases or to disulfide transferases to regulate the structure and function of intracellular proteins by modifying disulfide bonds between two cysteine residues in the side chain of the substrate proteins. The chloroplast Trx systems includes Trx and Trx-like proteins, ferredoxin (Fd)-dependent thioredoxin reductase (FTR) and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent thioredoxin C (NADPH Trx reductase C, NTRC). In addition to regulating the activity of stromal enzymes and transportation of chloroplast proteins by the Trx system, the chloroplast contains a reduction potential transfer pathway across the thylakoid membrane. The reduction potential of the substrate Trx is mediated by the transmembrane transporter and finally to the thylakoid lumenal protein. FTR and NTRC coordinate to regulate chloroplast homeostasis. This paper summarizes the regulatory mechanism of the chloroplast thioredoxin system that highlights the significance of the chloroplast Trx system in maintaining photosynthetic efficiency in plants.