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首页> 外文期刊>Infection and immunity >The thiol-activated toxin streptolysin O does not require a thiol group for cytolytic activity.
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The thiol-activated toxin streptolysin O does not require a thiol group for cytolytic activity.

机译：硫醇活化的毒素链球菌溶血素O不需要硫醇基团来具有细胞溶解活性。

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摘要

Site-directed mutagenesis of the TGC codon in a cloned streptolysin O (SLO) gene exchanged the single Cys residue in SLO for either Ala or Ser. The parent wild-type SLO (SLO.Cys-530) and the SLO.Ala-530 and SLO.Ser-530 mutant toxins, expressed in Escherichia coli, were purified and analyzed. Wild-type SLO.Cys-530 and the SLO.Ala-530 mutant showed no significant differences in their specific hemolytic activities, while the SLO.Ser-530 mutant had a reduced (ca. 25%), but still considerable, specific hemolytic activity as compared with that of wild-type SLO. The parent and mutant toxins extracted from lysed erythrocyte membranes had similar sedimentation profiles on sucrose density gradients, suggesting that the mutations did not affect the ability of SLO to form oligomers in membranes. These results show that the widely held assumption that the in vitro cytolytic activity of SLO requires an essential Cys residue is not true.
机译：克隆的链球菌溶血素O（SLO）基因中TGC密码子的定点诱变将SLO中的单个Cys残基交换为Ala或Ser。纯化并分析了在大肠杆菌中表达的亲本野生型SLO（SLO.Cys-530）和SLO.Ala-530和SLO.Ser-530突变毒素。野生型SLO.Cys-530和SLO.Ala-530突变体的特异性溶血活性无明显差异，而SLO.Ser-530突变体的特异性溶血活性降低（约25％），但仍相当可观活性与野生型SLO相比。从裂解的红细胞膜上提取的亲本和突变毒素在蔗糖密度梯度上具有相似的沉降曲线，这表明该突变不会影响SLO在膜上形成寡聚物的能力。这些结果表明，普遍认为SLO的体外细胞溶解活性需要必需的Cys残基是不正确的。

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