ENDONEXIN (ANNEXIN-IV)-MEDIATED LATERAL SEGREGATION OF PHOSPHATIDYLGLYCEROL IN PHOSPHATIDYLGLYCEROL PHOSPHATIDYLCHOLINE MEMBRANES
ENDONEXIN (ANNEXIN-IV)-MEDIATED LATERAL SEGREGATION OF PHOSPHATIDYLGLYCEROL IN PHOSPHATIDYLGLYCEROL PHOSPHATIDYLCHOLINE MEMBRANES
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DOI：
10.1021/bi00089a012
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发表时间：
1993-09-28
期刊：
影响因子：
2.9
通讯作者：
CREUTZ, CE
中科院分区：
文献类型：
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作者：
JUNKER, M;CREUTZ, CE
内啡肽（膜联蛋白IV）是膜联蛋白家族的一员，具有与纯脂质膜结合和以Ca2+依赖的方式聚集囊泡的能力。内啡肽似乎优先与某些类型的脂质相互作用，如PG/磷脂酰胆碱（PC）混合脂质膜中的磷脂酰甘油（PG）。这种优先结合应该导致PG脂质定位到内啡肽结合的膜区域。使用含有荧光团芘的PG衍生物进行了测试，该衍生物对分子碰撞频率具有荧光敏感性。pyrene-PG对内啡肽-膜结合的运动限制明显，内啡肽结合97% PG/3% pyrene-PG囊泡的准分子与单体（E/M）芘荧光比例降低。最大减少30%表明pyrenee - pg分子的平均扩散常数降低30%，或者假设仅外层单层脂质分子与内啡肽相互作用，平均扩散常数降低53%。在PC中含有5%和10%芘- pg的囊泡中，观察到在内毒素和10 mM（5%芘- pg）或2 mM（10%芘- pg）游离Ca2+的存在下，E/M分别增加14.2 +/- 1.8%和6.8 +/- 0.1%，可见脂质分离明显。在较高浓度的Ca2+ （5% pyrenee - pg为>0 mM， 10% pyrenee - pg为>2 mM）下，观察到较小的内啡肽依赖的E/M增加，因为内啡肽分子在高表面密度下竞争有限的pyrenee - pg池。内啡肽与混合脂质系统相互作用的性质暗示了膜联蛋白可能调节细胞膜结构的方式。
Endonexin (annexin IV) is a member of the annexin family of homologous proteins that share the ability to bind to pure lipid membranes and to aggregate vesicles in a Ca2+-dependent fashion. Endonexin appears to preferentially interact with certain types of lipids such as phosphatidylglycerol (PG) in PG/phosphatidylcholine (PC) mixed lipid membranes. Such preferential binding should result in localization of PG lipids to membrane regions where endonexin is bound. This was tested using a PG derivative containing the fluorophore pyrene, which exhibits fluorescence sensitive to molecular collision frequency. Motional restriction of pyrene-PG upon endonexin-membrane binding was evident from decreased ratios of excimer-to-monomer (E/M) pyrene fluorescence with endonexin binding to 97% PG/3% pyrene-PG vesicles. A maximum decrease of 30% suggests a 30% decrease in the average diffusion constant of pyrene-PG molecules or a 53% decrease assuming that only outer-monolayer lipid molecules interact with endonexin. In vesicles containing 5% and 10% pyrene-PG in PC, segregation of lipids was evident from observed increases in E/M of 14.2 +/- 1.8% and 6.8 +/- 0.1%, respectively, in the presence of endonexin and either 10 mM (5% pyrene-PG) or 2 mM (10% pyrene-PG) free Ca2+. At higher concentrations of Ca2+ (>10 mM for 5% pyrene-PG and >2 mM for 10% pyrene-PG), smaller endonexin-dependent increases in E/M are observed as endonexin molecules at high surface densities compete for the limited pool of pyrene-PG. The nature of these interactions of endonexin with mixed lipid systems has implications for the way annexins may modulate membrane structure in cells.