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首页> 外文期刊>Biochemistry >Mechanism and kinetics of delta-lysin interaction with phospholipid vesicles.
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Mechanism and kinetics of delta-lysin interaction with phospholipid vesicles.

机译：磷脂囊泡δ-溶酶相互作用的机理和动力学。

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摘要

Delta-lysin is a 26 amino acid, hemolytic peptide toxin secreted by Staphylococcus aureus. It has been reported to form an amphipathic helix upon binding to lipid bilayers and is often cited as a typical example of the barrel-stave model for pore formation in lipid bilayer membranes. However, the exact mechanism by which it lyses cells and the physical basis of its target specificity are still unknown. Moreover, the evidence for delta-lysin insertion and pore formation in the membrane stems largely from theoretical modeling of the toxin and lacks experimental confirmation. We investigated binding and insertion of delta-lysin into phospholipid bilayer vesicles. The kinetics of these processes were studied by stopped-flow fluorescence with two types of experiments: (a) carboxyfluorescein release from the vesicles upon peptide-vesicle interaction, with concomitant relief of dye self-quenching; (b) fluorescence energy transfer from the intrinsic tryptophan of the peptide to a membrane-bound lipid probe. We formulated a detailed kinetic mechanism with explicit molecular rate constants for peptide binding, association, and insertion, obtaining a quantitative description of the experimental results. delta-Lysin insertion is strongly dependent on the peptide-to-lipid ratio, suggesting that association of a critical number of monomers on the membrane is required for activity. However, we found no evidence for a stable membrane-inserted pore. Rather, the peptide appears to cross the membrane rapidly and reversibly and cause release of the lipid vesicle contents in this process.
机译：Delta-Lysin是由金黄色葡萄球菌分泌的26个氨基酸，溶血性毒素。据据报道，在结合脂质双层时形成两亲性螺旋，并且通常被称为脂质双层膜中孔隙形成模型的典型例子。然而，它裂解细胞和其目标特异性的物理基础的确切机制仍然未知。此外，薄膜中δ-溶胶插入和孔形成的证据主要来自毒素的理论建模并缺乏实验证实。我们研究了Delta-Lysin的结合和插入磷脂双层囊泡。通过用两种类型的实验进行停止流动荧光研究这些方法的动力学：（a）羧基荧光素从囊泡释放肽 - 囊泡相互作用，伴随染料自淬的粘附; （b）从肽的内在色氨酸的荧光能量转移到膜结合的脂质探针。我们制定了具有肽结合，关联和插入的明确分子速率常数的详细动力学机制，得到了实验结果的定量描述。 δ-溶素插入强烈依赖于肽 - 脂质比，表明活性需要临界数量的单体的关联。然而，我们发现没有证据稳定的膜插入孔。相反，肽似乎在该方法中迅速且可逆地穿过膜并引起脂质囊泡含量的释放。

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