A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts
A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts
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DOI：
10.1073/pnas.0511040103
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发表时间：
2006-02-21
影响因子：
11.1
通讯作者：
Buchanan, BB
中科院分区：
文献类型：
--
作者：
Balmer, Y;Vensel, WH;Buchanan, BB
越来越多的生物学过程通过巯基-二硫键交换的氧化还原来调节。这种机制在植物中特别普遍，其中几乎有200种蛋白质与硫氧还蛋白（Trx）（一种广泛分布的小型调节性二硫键蛋白）相关。目前的研究将Trx的调节扩展到淀粉体，这是异养植物组织中普遍存在的细胞器，在其他生物合成活动中，催化大量淀粉的合成和储存。利用蛋白质组学和免疫学方法，我们确定了铁氧还蛋白/Trx系统（铁氧还蛋白，铁氧还蛋白-Trx还原酶，和Trx），最初描述的叶绿体，从小麦淀粉胚乳中分离的造粉体的组件。铁氧还蛋白不像叶绿体那样被光还原，而是通过铁氧还蛋白-NADP还原酶被代谢产生的NADPH还原。然而，一旦被还原，铁氧还蛋白似乎就像叶绿体所建立的那样起作用，即，通过铁氧还蛋白-Trx还原酶和Trx（m型）。结合亲和层析和荧光巯基探针的蛋白质组学方法导致鉴定42种潜在的Trx靶蛋白，13种以前未识别，包括主要的膜转运蛋白（Brittle-1或ADP-葡萄糖转运蛋白）。除了淀粉代谢外，蛋白质还在一系列过程中发挥作用：脂质、氨基酸和核苷酸的生物合成;蛋白质折叠;以及几种杂项反应。结果表明，光最初在叶绿体中被识别为巯基信号，然后在运输到水槽期间被识别为糖，在那里它再次转化为巯基信号。通过这种方式，谷物中的造粉体反应可以与叶片中发生的光合作用相协调。
A growing number of processes throughout biology are regulated by redox via thiol-disulfide exchange. This mechanism is particularly widespread in plants, where almost 200 proteins have been linked to thioredoxin (Trx), a widely distributed small regulatory disulfide protein. The current study extends regulation by Trx to amyloplasts, organelles prevalent in heterotrophic plant tissues that, among other biosynthetic activities, catalyze the synthesis and storage of copious amounts of starch. Using proteomics and immunological methods, we identified the components of the ferredoxin/Trx system (ferredoxin, ferredoxin-Trx reductase, and Trx), originally described for chloroplasts, in amyloplasts isolated from wheat starchy endosperm. Ferredoxin is reduced not by light, as in chloroplasts, but by metabolically generated NADPH via ferredoxin-NADP reductase. However, once reduced, ferredoxin appears to act as established for chloroplasts, i.e., via ferredoxin-Trx reductase and a Trx (m-type). A proteomics approach in combination with affinity chromatography and a fluorescent thiol probe led to the identification of 42 potential Trx target proteins, 13 not previously recognized, including a major membrane transporter (Brittle-1 or ADP-glucose transporter). The proteins function in a range of processes in addition to starch metabolism: biosynthesis of lipids, amino acids, and nucleotides; protein folding; and several miscellaneous reactions. The results suggest a mechanism whereby light is initially recognized as a thiol signal in chloroplasts, then as a sugar during transit to the sink, where it is converted again to a thiol signal. In this way, amyloplast reactions in the grain can be coordinated with photosynthesis taking place in leaves.