Modulation of folding and assembly of the membrane protein bacteriorhodopsin by intermolecular forces within the lipid bilayer
Modulation of folding and assembly of the membrane protein bacteriorhodopsin by intermolecular forces within the lipid bilayer
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DOI：
10.1021/bi982322
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发表时间：
1999-07-20
期刊：
影响因子：
2.9
通讯作者：
Booth, PJ
中科院分区：
文献类型：
--
作者：
Curran, AR;Templer, RH;Booth, PJ
三种不同的脂类体系已经被用来研究脂双层中的物理化学力对完整膜蛋白细菌视紫红质折叠的影响。每个体系由含有两种脂类的脂泡组成，一种含有磷脂酰胆碱，另一种含有磷脂酰乙醇胺头基，但具有相同的碳氢链：L-α-1，2-二油酰基、L-α-1，2-二棕榈油酰基或L-α-1，2-二肉豆蔻基。增加磷脂酰乙醇胺类脂的摩尔分数增加了双层中每个单层小叶向水弯曲的愿望。这增加了这种单层的扭矩张力，当它们被约束为在囊泡双层中保持平坦时。因此，碳氢链区域的侧向压力增加，我们使用了来自芘标记的磷脂酰胆碱脂质的准分子荧光来探测这些压力的变化。我们发现，细菌视紫红质在100%磷脂酰胆碱的囊泡中再生到大约95%的产率。随着相应磷脂酰乙醇胺组分的摩尔分数的增加，再生率降低。产量的下降与脂链对复性蛋白质施加的侧向压力增加有关。我们认为，脂链压力的增加要么阻碍了细菌视黄素变性状态的插入，要么减缓了双层内的折叠步骤，以至于参与细菌视紫红质再生的中间体被有效地捕获。
Three different lipid systems have been developed to investigate the effect of physicochemical forces within the lipid bilayer on the folding of the integral membrane protein bacteriorhodopsin. Each system consists of lipid vesicles containing two lipid species, one with phosphatidylcholine and the other with phosphatidylethanolamine headgroups, but the same hydrocarbon chains: either L-alpha-1,2-dioleoyl, L-alpha-1,2-dipalmitoleoyl, or L-alpha-1,2-dimyristoyl. Increasing the mole fraction of the phosphatidylethanolamine lipid increases the desire of each monolayer leaflet in the bilayer to curve toward water. This increases the torque tension of such monolayers, when they are constrained to remain flat in the vesicle bilayer. Consequently, the lateral pressure in the hydrocarbon chain region increases, and we have used excimer fluorescence from pyrene-labeled phosphatidylcholine Lipids to probe these pressure changes. We show that bacteriorhodopsin regenerates to about 95% yield in vesicles of 100% phosphatidylcholine. The regeneration yield decreases as the mole fraction of the corresponding phosphatidylethanolamine component is increased. The decrease in yield correlates with the increase in lateral pressure which the Lipid chains exert on the refolding protein. We suggest that the increase in lipid chain pressure either hinders insertion of the denatured state of bacterioopsin into the bilayer or slows a folding step within the bilayer, to the extent that an intermediate involved in bacteriorhodopsin regeneration is effectively trapped.