Influence of membrane-lipid composition on translocation of nascent proteins in heated Escherichia coli.
Influence of membrane-lipid composition on translocation of nascent proteins in heated Escherichia coli.
复制标题
膜脂组成对加热大肠杆菌中新生蛋白质易位的影响。
DOI：
10.1016/0005-2736(87)90266-5
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Yatvin,MB
中科院分区：
文献类型：
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作者：
Yatvin,MB
在使用大肠杆菌的研究中表明，在热暴露后，新的蛋白质种类出现在外膜部分，同时可溶性和内膜部分的新生蛋白质损失。在对这一现象的各种解释中，温度引起的膜解体似乎是最有可能的。这表明，热量模拟了蛋白质信号序列在脂质双分子层上的作用，允许非含信号序列的蛋白质易位。为了验证这个假设，我们做了实验。coliK1060细胞是一种需要营养不良的不饱和脂肪酸，在生长过程中补充不同链长的脂肪酸，试图确定是否可以构建具有不同维持其双层结构能力的生物膜。其基本原理是，这种膜将使我们能够确定，当细胞受到一系列热损伤时，在相同温度下生长的细胞，补充16:1或20:1不饱和脂肪酸，是否会发生易位差异。在补充了长链脂肪酸的细胞中，蛋白质易位发生的程度更大，温度更低。用1 M盐、6 M尿素或高pH值处理外膜，以及在15至49°C的一系列温度范围内上下扫描确定荧光偏振值的研究表明，通过热转移到外膜的蛋白质是完整的。蛋白质易位可能代表了对环境改变的适应性反应，使细胞能够通过稳定外膜来应对压力。
In studies usingEscherichia coliwe have shown that new protein species appear in the outer membrane fraction with concomitant losses of nascent proteins from the soluble and inner membrane fractions following heat exposure. Of the various explanations for this phenomenon, temperature-induced membrane disorganization appeared the most likely. It is suggested that heat mimics the action of the signal sequence of a protein on the lipid bilayer allowing non-signal-sequence-containing proteins to be translocated. To test this hypothesis we grewE. coliK1060 cells, an unsaturated fatty acid requiring auxotroph, supplemented during growth with fatty acids of varying chain length in an attempt to determine whether biological membranes of varying ability to maintain their bilayer configuration could be constructed. The rationale being that such membranes would allow us to determine whether differences in translocation would occur in cells grown at the same temperature supplemented with either 16:1 or 20:1 unsaturated fatty acids when the cells were subjected to a series of thermal insults. Protein translocation occurred to a greater extent and at lower temperatures in cells supplemented with the longer chain fatty acid. Treatment of outer membranes with either 1 M salt, 6 M urea or high pH and studies determining fluorescent polarization values by scanning up and down through a series of temperatures ranging from 15 to 49°C indicate that the proteins translocated by heat to the outer membrane are integral. Protein translocation may represent an adaptive response to an altered environment enabling the cell to respond to stress by stabilizing its outer membrane.