Chloroplast Chaperonin: An Intricate Protein Folding Machine for Photosynthesis.
Chloroplast Chaperonin: An Intricate Protein Folding Machine for Photosynthesis.
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叶绿体伴侣蛋白：一种用于光合作用的复杂蛋白质折叠机器。
DOI：
10.3389/fmolb.2017.00098
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发表时间：
2017
影响因子：
5
通讯作者：
Liu C
中科院分区：
文献类型：
--
作者：
Zhao Q;Liu C
I组伴侣蛋白是一种大的圆柱形纳米机器，在细菌胞质、线粒体和叶绿体的蛋白质质量控制系统中发挥着中心枢纽的作用。在叶绿体中，由叶绿体核糖体新合成的蛋白质，在不同的胁迫下展开，或从细胞质中移位，都有发生异常折叠和聚集的风险。叶绿体伴侣蛋白系统帮助这些蛋白质折叠成它们的天然状态。核酮糖1，5-二磷酸羧化酶/加氧酶(Rubisco)是一种广为人知的蛋白质，由叶绿体伴侣蛋白折叠而成，负责在光合作用过程中将无机二氧化碳固定到有机碳水化合物中。叶绿体伴侣蛋白最初被鉴定为Rubisco结合蛋白。所有光合作用真核生物基因组都编码多个伴侣基因，这些基因可分为α和β亚型。与细菌和线粒体的同源低聚伴侣蛋白不同，叶绿体伴侣蛋白更为复杂，并以包含这两种亚型的错综复杂的杂寡体形式存在。I族伴侣蛋白需要在ATP和镁离子存在的情况下与可拆卸的盖状辅助伴侣蛋白进行适当的相互作用，以实现底物包裹和构象转变。除了典型的Cpn10类辅助伴侣蛋白外，叶绿体中还存在一种独特的辅助伴侣蛋白，它由两个串联的Cpn10结构域头尾相连组成。由于叶绿体被认为是各种环境胁迫的传感器，这种多样化的叶绿体伴侣蛋白系统有可能通过调节特定的底物或在转录和翻译后水平上进行调节来适应复杂的条件。本文从模式生物莱茵衣藻和拟南芥出发，对叶绿体伴侣蛋白系统的独特结构和功能的研究进展进行了综述。对叶绿体伴侣系统的了解可能最终导致真核细胞Rubisco在体外的成功重组。
Group I chaperonins are large cylindrical-shaped nano-machines that function as a central hub in the protein quality control system in the bacterial cytosol, mitochondria and chloroplasts. In chloroplasts, proteins newly synthesized by chloroplast ribosomes, unfolded by diverse stresses, or translocated from the cytosol run the risk of aberrant folding and aggregation. The chloroplast chaperonin system assists these proteins in folding into their native states. A widely known protein folded by chloroplast chaperonin is the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), an enzyme responsible for the fixation of inorganic CO2 into organic carbohydrates during photosynthesis. Chloroplast chaperonin was initially identified as a Rubisco-binding protein. All photosynthetic eucaryotes genomes encode multiple chaperonin genes which can be divided into α and β subtypes. Unlike the homo-oligomeric chaperonins from bacteria and mitochondria, chloroplast chaperonins are more complex and exists as intricate hetero-oligomers containing both subtypes. The Group I chaperonin requires proper interaction with a detachable lid-like co-chaperonin in the presence of ATP and Mg2+ for substrate encapsulation and conformational transition. Besides the typical Cpn10-like co-chaperonin, a unique co-chaperonin consisting of two tandem Cpn10-like domains joined head-to-tail exists in chloroplasts. Since chloroplasts were proposed as sensors to various environmental stresses, this diversified chloroplast chaperonin system has the potential to adapt to complex conditions by accommodating specific substrates or through regulation at both the transcriptional and post-translational levels. In this review, we discuss recent progress on the unique structure and function of the chloroplast chaperonin system based on model organisms Chlamydomonas reinhardtii and Arabidopsis thaliana. Knowledge of the chloroplast chaperonin system may ultimately lead to successful reconstitution of eukaryotic Rubisco in vitro.
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