Intrinsically Disordered Stress Protein COR15A Resides at the Membrane Surface during Dehydration
Intrinsically Disordered Stress Protein COR15A Resides at the Membrane Surface during Dehydration
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DOI：
10.1016/j.bpj.2017.06.027
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发表时间：
2017-08-08
影响因子：
3.4
通讯作者：
Hincha, Dirk K.
中科院分区：
文献类型：
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作者：
Bremer, Anne;Kent, Ben;Hincha, Dirk K.
来自温带气候地区的植物能够在暴露在零度以上的低温过程中提高它们的耐寒性，这一过程被称为冷驯化。在这个过程中，几个冷调节(COR)蛋白在细胞中积累。其中之一是COR15A，这是一种小的、内在无序的蛋白质，通过稳定细胞膜来帮助叶片耐寒。分离的蛋白质折叠成两亲性的α-螺旋，以响应增加的拥挤条件，例如高浓度的甘油。虽然有证据表明COR15A与膜直接相互作用，但蛋白质插入的方向和深度尚不清楚。此外，虽然已经确定了由于高渗透压浓度引起的折叠，但还没有研究蛋白质在逐渐脱水条件下的折叠反应。在这里，我们使用傅里叶变换红外光谱表明，COR15A在温和的脱水条件下(相对湿度97%，对应于零下3摄氏度的冰冻)就开始折叠成a螺旋，并且随着相对湿度的降低，折叠逐渐增加。在97%和75%RH下的中子衍射实验表明，CoR15A的存在对1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine膜的结构没有显著影响。然而，使用氢化POPC WE。可以清楚地证明COR15A与膜相互作用，并在头基区下方渗透到脂肪酰链区的上部。这一定位与我们的假设一致，即COR15A与膜的相互作用至少部分是由脂类和两亲性蛋白α-螺旋的疏水面之间的疏水相互作用驱动的。
Plants from temperate climate zones are able to increase their freezing tolerance during exposure to low, above zero temperatures in a process termed cold acclimation. During this process, several cold-regulated (COR) proteins are accumulated in the cells. One of them is COR15A, a small, intrinsically disordered protein that contributes to leaf freezing tolerance by stabilizing cellular membranes. The isolated protein folds into amphipathic a-helices in response to increased crowding conditions, such as high concentrations of glycerol. Although there is evidence for direct COR15A-membrane interactions, the orientation and depth of protein insertion were unknown. In addition, although folding due to high osmolyte concentrations had been established, the folding response of the protein under conditions of gradual dehydration had not been investigated. Here we show, using Fourier transform infrared spectroscopy, that COR15A starts to fold into a-helices already under mild dehydration conditions (97% relative humidity (RH), corresponding to freezing at -3 degrees C) and that folding gradually increases with decreasing RH. Neutron diffraction experiments at 97 and 75% RH established that the presence of COR15A had no significant influence on the structure of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. However, using deuterated POPC we. could clearly establish that COR15A interacts with the membranes and penetrates below the headgroup region into the upper part of the fatty acyl chain region. This localization is in agreement with our hypothesis that COR15A-membrane interaction is at least, in part, driven by a hydrophobic interaction between the lipids and the hydrophobic face of the amphipathic protein alpha-helix.