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首页> 外文期刊>Biochemistry >Interaction of theta-toxin (perfringolysin O), a cholesterol-binding cytolysin, with liposomal membranes: change in the aromatic side chains upon binding and insertion.
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Interaction of theta-toxin (perfringolysin O), a cholesterol-binding cytolysin, with liposomal membranes: change in the aromatic side chains upon binding and insertion.

机译：胆固醇结合型溶细胞素-毒素（穿孔菌素O）与脂质体膜的相互作用：结合和插入后，芳香族侧链发生变化。

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摘要

To understand the mechanism of membrane lysis by theta-toxin (perfringolysin O) from Clostridium perfringens, a cholesterol-binding, pore-forming cytolysin, we undertook a spectroscopic analysis of the structural changes that occur during the lytic process using lipid vesicles. In particular, the spectra were compared with those obtained using a modified theta-toxin, MC theta, that binds membrane cholesterol without forming oligomeric pores, thus bypassing the oligomerization step. The interaction of theta-toxin with liposomes composed of cholesterol and phosphatidylcholine but not with cholesterol-free liposomes caused a remarkable increase in the intensity of the tryptophan fluorescence emission spectra and ellipticity changes in the near- and far-UV CD peaks. A CD peak shift from 292 to 300 nm was specific for theta-toxin, suggesting oligomerization-specific changes occurring around tryptophan residues. Structural changes in the aromatic side chains were detected in the near-UV CD and fluorescence spectra upon MC theta-liposome interaction, although the far-UV CD spectra indicate that the beta-rich secondary structure of MC theta is well-conserved after membrane binding. Quenching of the intrinsic tryptophan fluorescence of MC theta by brominated lecithin/cholesterol liposomes suggests that theta-toxin inserts at least partly into membranes in the absence of oligomerization. These results indicate that regardless of oligomerization, the binding of theta-toxin to cholesterol induces partial membrane insertion and triggers conformational changes accompanied by aromatic side chain rearrangement with retention of secondary structure.(ABSTRACT TRUNCATED AT 250 WORDS)
机译：为了了解产气荚膜梭状芽孢杆菌（一种胆固醇结合的成孔性细胞溶素）中的theta毒素（产气荚膜溶血素O）的膜裂解机制，我们对使用脂囊泡的溶菌过程中发生的结构变化进行了光谱分析。特别地，将光谱与使用结合膜胆固醇而不形成低聚孔，从而绕过低聚步骤的修饰的θ-毒素MC theta获得的光谱进行比较。 θ毒素与胆固醇和磷脂酰胆碱组成的脂质体的相互作用，而不与不含胆固醇的脂质体的相互作用，导致色氨酸荧光发射光谱的强度显着增加，以及近紫外和远紫外CD峰的椭圆率变化。 CD峰从292 nm移到300 nm对theta-毒素具有特异性，表明色氨酸残基周围发生寡聚特异性变化。 MCθ-脂质体相互作用时，在近紫外CD和荧光光谱中检测到芳香族侧链的结构变化，尽管远紫外CD光谱表明膜结合后MCθ的富含β的二级结构非常保守。溴化卵磷脂/胆固醇脂质体淬灭MCθ的固有色氨酸荧光表明，在没有寡聚化的情况下，θ毒素至少部分插入膜中。这些结果表明，无论寡聚化如何，θ毒素与胆固醇的结合均会诱导部分膜插入并触发构象变化，并伴随芳香族侧链重排，并保留二级结构。（摘要摘录于250字）

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