Evaluation of diacylphospholipids as boundary lipids for bacteriorhodopsin from structural and functional aspects
Evaluation of diacylphospholipids as boundary lipids for bacteriorhodopsin from structural and functional aspects
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从结构和功能方面评价二酰磷脂作为细菌视紫红质的边界脂质
DOI：
10.1016/j.bbamem.2016.06.006
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Kawatake;S.;Umekawa;Y.;Matsuoka;S.;Murata;M.;Sonoyama;M.
用细菌视紫红质（bR）制备了含有多种二酰基磷脂的重构膜，使bR的固有磷脂含量降低到原来的24%，同时保留了bR的三聚体结构和光循环。采用具有不同头基的四种磷脂，磷脂酸（PA）、磷脂酰胆碱（PC）、磷脂酰甘油（PG）和磷脂酰丝氨酸（PS）进行重构。通过改变脂质-蛋白质的比例，这些磷脂与bR的相互作用，作为一个边界脂质，进行了评估，固态2 H/31 P NMR，圆二色性（CD），和激光闪光光解。~（31）PNMR结果表明，酸性磷脂酰甘油（PG）的头基与bR的相互作用比磷脂酰胆碱（PC）的头基更强。CD分析表明，bR的三维结构保留在所有的磷脂-bR制剂在低和中等脂质含量。酸性脂质PA，PG和PS恢复的bR的光循环活性的程度相当（或略低于）的紫膜，而PC引起的bR光循环效率显着降低。在具有不同脂肪酰基的PG中，具有单不饱和脂质和双不饱和脂质的PG倾向于保持光循环效率，而完全饱和脂质则不然。这些结果表明，酸性不饱和磷脂，特别是二油酰磷脂酰甘油（DOPG），具有更高的亲和力bR和有效地恢复其立体结构。目前的研究表明，在DOPG双分子层中重构的bR可能被用作光谱研究脂质-bR与膜整合α-螺旋相互作用的模型系统，并可能用于类似类型的膜蛋白。
Reconstituted membranes with diverse diacylphospholipids were prepared by using bacteriorhodopsin (bR) in which the intrinsic lipid content was decreased to 24% of the original while the trimeric structure and photocycle of bR were retained. Four phospholipids with a different headgroup, phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylserine (PS), were adopted for reconstitution. By varying the lipid-protein ratios, the interactions of these phospholipids with bR, as a boundary lipid, were evaluated by solid state2H/31P NMR, circular dichroism (CD), and laser-flash photolysis. The31P NMR results revealed that the headgroup of acidic phosphatidylglycerol (PG) interacts more strongly with bR than that of phosphatidylcholine (PC). CD analysis indicated that the trimetric structure of bR was retained in all the phospholipid-bR preparations at low and medium lipid contents. Acidic lipids PA, PG and PS restored the photocycle activity of bR to an extent comparable to (or slightly lower than) that of the purple membrane while PC caused a marked reduction of the bR photocycle efficiency. Among PGs with different fatty acyl groups, those with mono- and di-unsaturated lipids tended to preserve the photocycle efficiency, whereas the fully saturated lipid did not. These results show that acidic unsaturated phospholipids, particularly dioleoylphosphatidylglycerol (DOPG), have higher affinity for bR and efficiently restore its trimetric structure. The present study suggests that bR reconstituted in DOPG bilayers may possibly be used as a model system for spectroscopic investigations of the lipid-bR interactions with the membrane-integral α-helices, and potentially for a similar type of membrane proteins.