Navarro-Retamal Carlos, Bremer Anne, Alzate-Morales Jans, Caballero Julio, Hincha Dirk K, González Wendy, Thalhammer Anja
Center for Bioinformatics and Molecular Simulations, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile.
Phys Chem Chem Phys. 2016 Oct 7;18(37):25806-16. doi: 10.1039/c6cp02272c. Epub 2016 Jun 3.
The LEA (late embryogenesis abundant) proteins COR15A and COR15B from Arabidopsis thaliana are intrinsically disordered under fully hydrated conditions, but obtain α-helical structure during dehydration, which is reversible upon rehydration. To understand this unusual structural transition, both proteins were investigated by circular dichroism (CD) and molecular dynamics (MD) approaches. MD simulations showed unfolding of the proteins in water, in agreement with CD data obtained with both HIS-tagged and untagged recombinant proteins. Mainly intramolecular hydrogen bonds (H-bonds) formed by the protein backbone were replaced by H-bonds with water molecules. As COR15 proteins function in vivo as protectants in leaves partially dehydrated by freezing, unfolding was further assessed under crowded conditions. Glycerol reduced (40%) or prevented (100%) unfolding during MD simulations, in agreement with CD spectroscopy results. H-bonding analysis indicated that preferential exclusion of glycerol from the protein backbone increased stability of the folded state.
拟南芥中的胚胎后期丰富（LEA）蛋白COR15A和COR15B在完全水合条件下是内在无序的，但在脱水过程中会形成α-螺旋结构，复水后这种结构是可逆的。为了理解这种不寻常的结构转变，通过圆二色性（CD）和分子动力学（MD）方法对这两种蛋白进行了研究。MD模拟显示蛋白在水中展开，这与用带HIS标签和不带标签的重组蛋白获得的CD数据一致。主要由蛋白质主链形成的分子内氢键（H键）被与水分子的H键所取代。由于COR15蛋白在体内作为叶片中因冷冻而部分脱水的保护剂发挥作用，因此在拥挤条件下进一步评估了其展开情况。甘油在MD模拟过程中减少了（40%）或阻止了（100%）展开，这与CD光谱结果一致。氢键分析表明，甘油从蛋白质主链中的优先排除增加了折叠态的稳定性。
