Tolleter Dimitri, Jaquinod Michel, Mangavel Cécile, Passirani Catherine, Saulnier Patrick, Manon Stephen, Teyssier Emeline, Payet Nicole, Avelange-Macherel Marie-Hélène, Macherel David
Unité Mixte de Recherche 1191, Physiologie Moléculaire des Semences, Université d'Angers/Institut National d'Horticulture/Institut National de la Recherche Agronomique, Angers F-49045, France.
Plant Cell. 2007 May;19(5):1580-9. doi: 10.1105/tpc.107.050104. Epub 2007 May 25.
Few organisms are able to withstand desiccation stress; however, desiccation tolerance is widespread among plant seeds. Survival without water relies on an array of mechanisms, including the accumulation of stress proteins such as the late embryogenesis abundant (LEA) proteins. These hydrophilic proteins are prominent in plant seeds but also found in desiccation-tolerant organisms. In spite of many theories and observations, LEA protein function remains unclear. Here, we show that LEAM, a mitochondrial LEA protein expressed in seeds, is a natively unfolded protein, which reversibly folds into alpha-helices upon desiccation. Structural modeling revealed an analogy with class A amphipathic helices of apolipoproteins that coat low-density lipoprotein particles in mammals. LEAM appears spontaneously modified by deamidation and oxidation of several residues that contribute to its structural features. LEAM interacts with membranes in the dry state and protects liposomes subjected to drying. The overall results provide strong evidence that LEAM protects the inner mitochondrial membrane during desiccation. According to sequence analyses of several homologous proteins from various desiccation-tolerant organisms, a similar protection mechanism likely acts with other types of cellular membranes.
很少有生物能够承受干燥胁迫；然而，种子普遍具有耐旱性。无水生存依赖于一系列机制，包括积累应激蛋白，如胚胎后期丰富（LEA）蛋白。这些亲水性蛋白在植物种子中很突出，但也存在于耐旱生物中。尽管有许多理论和观察结果，但LEA蛋白的功能仍不清楚。在这里，我们表明，LEAM是一种在种子中表达的线粒体LEA蛋白，是一种天然未折叠的蛋白，在干燥时可逆地折叠成α螺旋。结构建模显示，它与哺乳动物中包裹低密度脂蛋白颗粒的载脂蛋白A类两亲性螺旋类似。LEAM似乎会因几个有助于其结构特征的残基发生脱酰胺和氧化而自发修饰。LEAM在干燥状态下与膜相互作用，并保护经受干燥的脂质体。总体结果提供了有力证据，表明LEAM在干燥过程中保护线粒体内膜。根据对来自各种耐旱生物的几种同源蛋白的序列分析，类似的保护机制可能作用于其他类型的细胞膜。
