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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Effects of lactose permease of Escherichia coli on the anisotropy and electrostatic surface potential of liposomes.
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Effects of lactose permease of Escherichia coli on the anisotropy and electrostatic surface potential of liposomes.

机译：大肠杆菌的乳糖通透酶对脂质体的各向异性和静电表面电势的影响。

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摘要

The membrane transport protein lactose permease (LacY), a member of the Major Facilitator Superfamily (MFS) containing twelve membrane-spanning segments connected by hydrophilic loops, was reconstituted in liposomes of: (i) 1,2-dimyristoyl-sn-glycero-3-phosphocoline (DMPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in equimolar proportions; and (ii) Escherichia coli total lipid extract. The structural order of the lipid membranes, in the presence and absence of LacY, was investigated using steady-state fluorescence anisotropy. The features of the anisotropy curves obtained with 1,6-phenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluene sulfonate (TMA-DPH) evidenced: (i) the insertion of LacY into the bilayer; and (ii) a surface effect on the membranes. The most dramatic effects were observed when LacY was reconstituted in the E. coli lipid matrix. The effect of the protein on the electrostatic surface potential of each bilayer was also examined using a fluorescent pH indicator, 4-Heptadecyl-7-hydroxycoumarin (HHC). Changes in surface potential were enhanced in the presence of the substrate (i.e. lactose) only when the lipid matrices were charged. These results suggest a role for charged phospholipids (i.e. phosphatidylethanolamine or phosphatidylglycerol) in proton transfer to the amino acids involved in substrate translocation.
机译：膜转运蛋白乳糖通透酶（LacY）是主要促进剂超家族（MFS）的成员，其包含通过亲水环连接的十二个跨膜区段，在以下脂质体中重构：（i）1,2-二肉豆蔻酰基-sn-甘油-等摩尔比例的3-磷酸代磷酸酯（DMPC）和1-棕榈酰-2-油酰基-sn-甘油-3-磷酸胆碱（POPC）; （ii）大肠杆菌总脂质提取物。使用稳态荧光各向异性研究了在存在和不存在LacY的情况下脂质膜的结构顺序。 1,6-苯基-1,3,5-己三烯（DPH）和1-（4-三甲基铵苯基）-6-苯基-1,3,5-己三烯对甲苯磺酸盐（TMA）获得的各向异性曲线的特征-DPH）证明：（i）LacY插入双层; （ii）对膜的表面作用。当LacY在大肠杆菌脂质基质中重构时，观察到最显着的影响。还使用荧光pH指示剂4-Heptadecyl-7-hydroxycoumarin（HHC）检查了蛋白质对每个双层静电表面电势的影响。仅当脂质基质带电时，在存在底物（即乳糖）的情况下，表面电势的变化才会增强。这些结果表明带电荷的磷脂（即磷脂酰乙醇胺或磷脂酰甘油）在质子转移到涉及底物易位的氨基酸中的作用。

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