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首页> 外文期刊>Journal of Molecular Biology >Acidic pH-induced membrane insertion of colicin A into E. Coli natural lipids probed by site-directed Spin labeling
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Acidic pH-induced membrane insertion of colicin A into E. Coli natural lipids probed by site-directed Spin labeling

机译：酸性pH诱导大肠菌素A插入大肠杆菌的天然脂质膜中，通过定点旋转标记探测

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Abstract Colicin A is a pore-forming toxin that forms a voltage-gated channel in the inner membrane of the target bacteria. The structures of the closed and open channel states of membrane-bound colicin A are not resolved. In the present site-directed spin-labeling study, the insertion-competent state of colicin A is provoked by an acidic pH jump prior to the insertion into liposomes prepared from Escherichia coli natural lipids. The membrane-bound colicin A is able to open a voltage-dependent channel as demonstrated by the efflux of tempophosphate spin label from the lumen of liposomes. The EPR spectra of spin-labeled colicin A variants in the membrane-bound closed channel state reveal a conformational equilibrium with resolved interhelical tertiary contacts. The spin label accessibility and polarity profiles suggest the amphipathic helices (H1-H7 and H10) to be located in the membrane close to the membrane-water interface and the hydrophobic hairpin (H8 and H9) to be immersed more deeply in the membrane.
机译：摘要Colicin A是一种成孔毒素，可在目标细菌的内膜上形成电压门控通道。膜结合的大肠菌素A的封闭和开放通道状态的结构无法解析。在目前的定点旋转标记研究中，大肠菌素A的插入能力状态是在插入由大肠杆菌天然脂质制备的脂质体之前，通过酸性pH跃迁引起的。膜结合的大肠菌素A能够打开电压依赖性通道，如脂质体内腔中临时磷酸盐自旋标记的流出所证明。膜结合的封闭通道状态下自旋标记的大肠菌素A变体的EPR光谱显示构象平衡，其中螺旋间三级接触已解决。自旋标记的可及性和极性分布表明两亲性螺旋（H1-H7和H10）位于膜中，靠近膜-水界面，疏水性发夹（H8和H9）更深地浸入膜中。

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