Binding of monovalent cations to phosphatidylserine and modulation of Ca2+- and Mg2+-induced vesicle fusion.
Binding of monovalent cations to phosphatidylserine and modulation of Ca2+- and Mg2+-induced vesicle fusion.
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单价阳离子与磷脂酰丝氨酸的结合以及 Ca2 和 Mg2 诱导的囊泡融合的调节。
DOI：
10.1016/0005-2736(83)90271-7
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Bentz,J
中科院分区：
文献类型：
--
作者：
Nir,S;Düzgüneş,N;Bentz,J
通过使用 Tb/吡啶二羧酸测定法监测融合囊泡内部区室的混合，研究了几种单价阳离子对 Ca 2+ 诱导的超声处理磷脂酰丝氨酸 (PS) 囊泡聚集和融合的影响。直接测定伴随Ca 2+ 诱导的囊泡融合的荧光Tb-吡啶二羧酸复合物的解离，这是由于内容物的渗漏和介质进入囊泡所致。当培养基仅含有单价阳离子（pH 7.4）时，无论阳离子浓度或囊泡是否聚集，PS囊泡都不会融合。数据的质量作用动力学分析提供了聚集速率 C 11 和融合速率本身 f 11 的估计值。f 11 的值随着单价阳离子浓度的降低而急剧增加，并且主要由每 PS 的 Ca 2+ 或 Mg 2+ 的结合比率决定。对于 300 mM 的单价阳离子，融合本身本质上是整个融合过程的速率限制，并且对于结合最少的单价阳离子，f 11 的值明显更大，即根据顺序四甲基铵 > K+> Na+> Li+。当单价阳离子浓度为 100 mM 或更低时，聚集对融合具有速率限制，总体初始融合速率由聚集和融合速率之间的相互作用决定。在快速聚集的条件下，Ca 2+ 诱导的小 PS 囊泡融合可以在几毫秒或更短的时间内发生。
The effect of several monovalent cations on the Ca 2+-induced aggregation and fusion of sonicated phosphatidylserine (PS) vesicles is studied by monitoring the mixing of internal compartments of the fusing vesicles using the Tb/dipicolinic acid assay. The dissociation of the fluorescent Tb-dipicolinate complex which accompanies Ca 2+-induced vesicle fusion is determined directly and is due to leakage of contents and entry of medium into vesicles. PS vesicles do not fuse when the medium contains only monovalent cations (at pH 7.4), regardless of the cation concentration or whether there is aggregation of the vesicles. A mass-action kinetic analysis of the data provides estimates for the rate of aggregation, C 11, and for the rate of fusion per se, f 11. Values of f 11 increase dramatically with reduction in monovalent cation concentration and are primarily determined by binding ratios of Ca 2+ or Mg 2+ per PS. With 300 mM of monovalent cations, the fusion per se is essentially rate-limiting to the overall fusion process and values of f 11 are significantly larger with the monovalent cations which bind the least, ie, according to the sequence tetramethylammonium> K+> Na+> Li+. With monovalent cations in concentrations of 100 mM or less, the aggregation is rate-limiting to the fusion and the overall initial fusion rates are determined by an interplay between aggregation and fusion rates. Under conditions of fast aggregation, the Ca 2+-induced fusion of small PS vesicles can occur within milliseconds or less.