Stability of KcsA tetramer depends on membrane lateral pressure
Stability of KcsA tetramer depends on membrane lateral pressure
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DOI：
10.1021/bi036129d
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发表时间：
2004-04-13
期刊：
影响因子：
2.9
通讯作者：
de Kruijff, B
中科院分区：
文献类型：
--
作者：
van den Brink-van der Laan, E;Chupin, V;de Kruijff, B
钾通道KCSA形成非常稳定的四聚体。尽管有很高的稳定性，但已证明仿膜溶剂2，2，2-三氟乙醇(TFE)可以诱导四聚体解离[Valiyaveetil，F.I.，et al.(2002年)生物化学41,10771-7，和德默斯，J.A.，等人。(2003)FEBS Lett.541、69-77]。在这里，我们研究了TFe对在不同脂类体系中重组的KCSA四聚体的结构和低聚状态的影响。结果表明，TFE改变了KCSA的二级和三级结构，在所有使用的体系中都能解离KCSA四聚体。与洗涤剂胶束相比，四聚体由脂双层稳定。稳定的程度取决于脂质的性质：非双层脂质磷脂酰乙醇胺(PE)有很强的稳定作用，而带电的磷脂酰甘油(PG)与磷脂酰胆碱(PC)相比没有明显的稳定作用。为了了解脂类如何稳定KCSA对抗TFE诱导的四聚体解离，我们还利用P-31和H-2核磁共振研究了TFE对不同脂类体系中双层结构的影响。观察到的脂质依赖性与四聚体稳定性相似：与PC相比，PE增加了双层稳定性，而PG的行为与PC相似。此外，还发现TFE对酰基链的有序性有很大影响。结果表明，TFe主要嵌入在膜界面。我们认为，脂质双层通过在酰基链区域施加侧向压力来稳定KCSA四聚体，并且当存在类似PE的非双层脂质时，这种稳定作用增强。
The potassium channel KcsA forms an extremely stable tetramer. Despite this high stability, it has been shown that the membrane-mimicking solvent 2,2,2-trifluoroethanol (TFE) can induce tetramer dissociation [Valiyaveetil, F. I., et al. (2002) Biochemistry 41, 10771-7, and Demmers, J. A. A., et al. (2003) FEBS Lett. 541, 69-77]. Here we have studied the effect of TFE on the structure and oligomeric state of the KcsA tetramer, reconstituted in different lipid systems. It was found that TFE changes the secondary and tertiary structure of KcsA and that it can dissociate the KcsA tetramer in all systems used. The tetramer is stabilized by a lipid bilayer as compared to detergent micelles. The extent of stabilization was found to depend on the nature of the lipids: a strong stabilizing effect of the nonbilayer lipid phosphatidylethanolamine (PE) was observed, but no effect of the charged phoshosphatidylglycerol (PG) as compared to phosphatidylcholine (PC) was found. To understand how lipids stabilize KcsA against TFE-induced tetramer dissociation, we also studied the effect of TFE on the bilayer organization in the various lipid systems, using P-31 and H-2 NMR. The observed lipid dependency was similar as was found for tetramer stabilization: PE increased the bilayer stability as compared to PC, while PG behaved similar to PC. Furthermore, it was found that TFE has a large effect on the acyl chain ordering. The results indicate that TFE inserts primarily in the membrane interface. We suggest that the lipid bilayer stabilizes the KcsA tetramer by the lateral pressure in the acyl chain region and that this stabilizing effect increases when a nonbilayer lipid like PE is present.