Duncan J L, Buckingham L
Biochim Biophys Acta. 1981 Oct 20;648(1):6-12. doi: 10.1016/0005-2736(81)90119-x.
The effect of the bacterial cytolytic toxin, streptolysin S, on liposomes composed of various phospholipids was investigated. Large unilamellar vesicles containing [14C]sucrose were prepared by reverse-phase evaporation, and membrane damage produced by the toxin was measured by following the release of labeled marker. The net charge of the liposomes had little or no effect on their susceptibility to steptolysin S and the toxin was about equally effective on liposomes composed of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylglycerol. Experiments with liposomes composed of synthetic phospholipids showed that the ability of the toxin to produce membrane damage depended on the degree of unsaturation of the fatty acyl chains. The order of sensitivity was C18 : 2 phosphatidylcholine greater than C18: I phosphatidylcholine greater than C18 : 0 phosphatidylcholine = C16 : 0 phosphatidylcholine. Liposomes containing the latter two phospholipids were virtually unaffected by streptolysin S, and experiments with C18 : 0 phosphatidylcholine suggested that toxin activity does not bind to liposomes composed of phospholipids with saturated fatty acyl chains. The inclusion of 40 mol% cholesterol in C16 : 0 phosphatidylcholine and C18 : 0 phosphatidylcholine liposomes made these vesicles sensitive to streptolysin S. Egg phosphatidylcholine liposomes, which were unaffected at 0 degrees C and 4 degrees C became susceptible to the toxin at these temperatures when cholesterol was included. Liposomes composed of C14 : 0 phosphatidylcholine were unaffected by streptolysin S at temperatures below the chain-melting transition temperature (23 degrees C) of this phospholipid, but became increasingly susceptible above this temperature. The results suggest that the fluidity of the phospholipid hydrocarbon chains in the membrane is important in streptolysin S action.
研究了细菌溶细胞毒素链球菌溶血素S对由各种磷脂组成的脂质体的作用。通过反相蒸发制备了含有[14C]蔗糖的大单层囊泡，并通过追踪标记物的释放来测量毒素产生的膜损伤。脂质体的净电荷对其对链球菌溶血素S的敏感性影响很小或没有影响，并且该毒素对由磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰丝氨酸和磷脂酰甘油组成的脂质体的作用大致相同。用合成磷脂组成的脂质体进行的实验表明，毒素产生膜损伤的能力取决于脂肪酰链的不饱和程度。敏感性顺序为：C18:2磷脂酰胆碱＞C18:1磷脂酰胆碱＞C18:0磷脂酰胆碱 = C16:0磷脂酰胆碱。含有后两种磷脂的脂质体实际上不受链球菌溶血素S的影响，并且用C18:0磷脂酰胆碱进行的实验表明，毒素活性不与由具有饱和脂肪酰链的磷脂组成的脂质体结合。在C16:0磷脂酰胆碱和C18:0磷脂酰胆碱脂质体中加入40摩尔%的胆固醇使这些囊泡对链球菌溶血素S敏感。在0℃和4℃时不受影响的鸡蛋磷脂酰胆碱脂质体，当加入胆固醇时在这些温度下变得易受毒素影响。由C14:0磷脂酰胆碱组成的脂质体在低于该磷脂链熔化转变温度（23℃）时不受链球菌溶血素S的影响，但在该温度以上变得越来越敏感。结果表明，膜中磷脂烃链的流动性在链球菌溶血素S的作用中很重要。
