Arabidopsis Cor15am is a chloroplast stromal protein that has cryoprotective activity and forms oligomers
Arabidopsis Cor15am is a chloroplast stromal protein that has cryoprotective activity and forms oligomers
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DOI：
10.1104/pp.106.094581
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发表时间：
2007-05-01
期刊：
影响因子：
7.4
通讯作者：
Inaba, Takehito
中科院分区：
文献类型：
--
作者：
Nakayama, Katsuhiro;Okawa, Kumiko;Inaba, Takehito
许多植物在一定时间内暴露于不结冰的温度下时，其抗冻性会增强。这个过程被称为冷驯化，使植物保护自己免受冻害。冷驯化诱导产生了多种多肽，其中一种是由拟南芥（Arabidopsis thaliana）中的COR 15 A编码的多肽。先前的研究表明，COR 15 A基因编码一种小的质体靶向多肽，该多肽被加工成成熟形式，称为Cor 15 am。在这项研究中，我们更详细地研究了Cor 15 am的生化特性和活性。我们提供的证据表明，Cor 15 AM本地化几乎完全叶绿体基质。此外，冷调节积累的Cor 15 am的叶绿体功能的影响。凝胶过滤层析和蛋白质交联都揭示了Cor 15 am在叶绿体基质中形成低聚物。虽然Cor 15 am积累响应于低温，冷驯化是不是Cor 15 am的寡聚化的先决条件。结构分析表明，Cor 15 am由有序结构和随机结构组成，在煮沸和冻融处理后仍能保持溶解状态，结构变化较小。重组Cor 15 am表现出对冷冻不稳定酶L-乳酸脱氢酶的体外冷冻保护作用。此外，Cor 15 am能够在体外与L-乳酸脱氢酶结合，并在体内与潜在的基质底物结合。在这些结果的基础上，我们提出，拟南芥Cor 15 am是一种低温保护蛋白，形成低聚物的叶绿体基质，和Cor 15 am与其底物的直接关联是其低温保护机制的一部分。
Many plants acquire increased freezing tolerance when they are exposed to nonfreezing temperatures of a certain duration. This process is known as cold acclimation and allows plants to protect themselves from freezing injury. A wide variety of polypeptides are induced during cold acclimation, among which is one encoded by COR15A in Arabidopsis (Arabidopsis thaliana). Previous studies showed that the COR15A gene encodes a small, plastid-targeted polypeptide that is processed to a mature form called Cor15am. In this study, we examined the biochemical properties and activities of Cor15am in more detail. We provide evidence that Cor15am localizes almost exclusively to the chloroplast stroma. In addition, the cold-regulated accumulation of Cor15am is affected by chloroplast functionality. Both gel-filtration chromatography and protein cross-linking reveal that Cor15am forms oligomers in the stroma of chloroplasts. Although Cor15am accumulates in response to low temperature, cold acclimation is not a prerequisite for oligomerization of Cor15am. Structural analysis suggests that Cor15am is composed of both ordered and random structures, and can stay soluble with small structural change after boiling and freeze-thaw treatments. Recombinant Cor15am exhibits in vitro cryoprotection of a freeze-labile enzyme, L-lactate dehydrogenase. Furthermore, Cor15am is capable of associating with L-lactate dehydrogenase in vitro and with potential stromal substrates in vivo. On the basis of these results, we propose that Arabidopsis Cor15am is a cryoprotective protein that forms oligomers in the chloroplast stroma, and that direct association of Cor15am with its substrates is part of its cryoprotective mechanism.