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首页> 外文期刊>Biochemistry >Secretion and circular dichroism analysis of the C-terminal signal peptides of HlyA and LktA.
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Secretion and circular dichroism analysis of the C-terminal signal peptides of HlyA and LktA.

机译：HlyA和LktA的C端信号肽的分泌和圆二色性分析。

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摘要

The secretion of the 107 kDa hemolysin A (HlyA) from Escherichia coli is mediated by membrane proteins hemolysin B (HlyB) and hemolysin D (HlyD). The signal for transport has been mapped to the C-terminal 60 amino acids of the HylA molecule. We have shown previously that the C-terminal 70 amino acids of leukotoxin (LktA) from Pasteurella hemolytica can substitute functionally for the HlyA signal sequence. This 70 amino acid peptide contains little primary sequence similarity to the HlyA signal sequence, and we have hypothesized that these signal sequences assume a similar higher-order structure which is recognized by the HlyB/D transporter. In the present study, we have expressed and purified small peptides containing the C-terminal 61 amino acids of HlyA and the C-terminal 70 amino acids of LktA. We show that these signal peptides are sufficient for secretion from E. coli in a HlyB/D dependent manner. Circular dichroism analyses show that both molecules exhibit common biophysical properties. In aqueous solution, they appear to be mainly unstructured, but in a membrane mimetic environment they assume a helical secondary structure. The conformational change observed for both peptides going from an aqueous to a membrane mimetic environment may be an important feature of these signal sequences necessary for their recognition and transport.
机译：大肠杆菌分泌的107 kDa溶血素A（HlyA）由膜蛋白溶血素B（HlyB）和溶血素D（HlyD）介导。用于运输的信号已定位到HylA分子的C末端60个氨基酸。先前我们已经表明，溶血巴斯德氏菌白细胞毒素（LktA）的C端70个氨基酸可以在功能上替代HlyA信号序列。该70个氨基酸的肽与HlyA信号序列几乎没有一级序列相似性，并且我们已经假设这些信号序列具有类似的高级结构，该结构被HlyB / D转运蛋白识别。在本研究中，我们已经表达和纯化了含有HlyA的C末端61个氨基酸和LktA的C末端70个氨基酸的小肽。我们显示这些信号肽足以以HlyB / D依赖方式从大肠杆菌分泌。圆二色性分析表明，两种分子均表现出共同的生物物理特性。在水溶液中，它们似乎主要是无结构的，但在膜模拟环境中，它们呈螺旋二级结构。从水样环境到膜模拟环境这两种肽观察到的构象变化可能是这些信号序列识别和运输所必需的重要特征。

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