Irreversible loss of membrane-binding activity of Listeria-derived cytolysins in non-acidic conditions:: a distinct difference from allied cytolysins produced by other Gram-positive bacteria
Irreversible loss of membrane-binding activity of Listeria-derived cytolysins in non-acidic conditions:: a distinct difference from allied cytolysins produced by other Gram-positive bacteria
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DOI：
10.1099/mic.0.2007/005843-0
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发表时间：
2007-07-01
期刊：
影响因子：
2.8
通讯作者：
Mitsuyama, Masao
中科院分区：
文献类型：
--
作者：
Nomura, Takamasa;Kawamura, Ikuo;Mitsuyama, Masao
李斯特菌溶血素O（Listeriolysin O，LLO）是单核细胞增生李斯特菌（Listeria monocytogenes）的主要毒力因子，是胆固醇依赖性溶细胞素（cholesterol-dependent cytolysin，CDC）家族的成员之一。LLO在弱酸性条件下被激活;然而，LLO溶细胞活性的这种pH依赖性表达的分子机制知之甚少。在本研究中，制备了包括LLO、ivanolysin O（ILO）、seeligeriolysin O（LSO）、pneumolysin（PFO）、streptolysin O（SLO）和perfringolysin O（PFO）的CDC作为重组蛋白，并检测了它们在不同pH条件下处理后的功能变化。溶血性和膜胆固醇结合活性不受影响，SLO和PFO在任何pH值检查。相比之下，所有李斯特菌衍生的溶细胞素LLO、ILO和LSO仅在酸性pH下有活性，并且在中性或碱性条件下迅速失活。一旦失活，即使通过向下的pH变化，LLO也不能再活化。在中性或碱性条件下处理的LLO的疏水性增加。这些数据表明，溶细胞活性的pH依赖性损失似乎是由于结构域4的不可逆结构变化导致靶膜胆固醇结合的损失。
Listeriolysin O (LLO), a member of the cholesterol-dependent cytolysin (CDC) family, is a major virulence factor of Listeria monocytogenes and contributes to bacterial escape from intracellular killing of macrophages. LLO is activated under weakly acidic conditions; however, the molecular mechanism of this pH-dependent expression of cytolytic activity of LLO is poorly understood. In this study, CDCs including LLO, ivanolysin O (ILO), seeligeriolysin O (LSO), pneumolysin (PLY), streptolysin O (SLO) and perfringolysin O (PFO) were prepared as recombinant proteins and examined for their functional changes after treatment under various pH conditions. Haemolytic and membrane cholesterol-binding activities were not affected in PLY, SLO and PFO at any pH examined. By contrast, all the Listeria-derived cytolysins, LLO, ILO and LSO, were active only at an acidic pH and rapidly inactivated under neutral or alkaline conditions. Once inactivated, LLO could not be reactivated even by a downward pH shift. The hydrophobicity of LLO treated at neutral or alkaline pH was increased. These data suggested that the pH-dependent loss of cytolytic activity appeared to be due to irreversible structural changes of domain 4 that resulted in the loss of target membrane cholesterol binding.