Alpha-synuclein association with phosphatidylglycerol probed by lipid spin labels.
Alpha-synuclein association with phosphatidylglycerol probed by lipid spin labels.
复制标题
通过脂质自旋标记探测α-突触核蛋白与磷脂酰甘油的关联。
作者：
Muthu Ramakrishnan;P. Jensen;D. Marsh
α-突触核蛋白是一种小型突触前蛋白，与帕金森病的发生有关。α-突触核蛋白在胞质和囊泡结合状态之间分配，其中膜结合伴随着在其他非结构化蛋白质的N-末端部分形成两亲性螺旋。已经广泛研究了与囊泡样脂质体结合对α-突触核蛋白的影响，但关于α-突触核蛋白对膜的影响知之甚少。α-突触核蛋白与磷脂酰甘油膜的相互作用在这里进行了研究，通过使用自旋标记的脂质物种和电子自旋共振（ESR）光谱，允许对膜脂质的影响进行详细的分析。α-突触核蛋白的膜结合干扰了磷脂酰甘油双层中自旋标记脂质的ESR谱，但磷脂酰胆碱不干扰。这种相互作用在高离子强度下受到抑制。链段运动在磷脂酰甘油sn-2链中自旋标记的所有位置处受到阻碍，同时仍保留流体磷脂膜的链柔性梯度特性。没有观察到由蛋白质渗透到膜的疏水内部引起的脂质链的直接运动限制。饱和发生在蛋白质/脂质比对应于大约36个脂质/蛋白质添加。当与磷脂酰甘油膜结合时，α-突触核蛋白表现出与不同磷脂自旋标记物相互作用的选择性，顺序如下：硬脂酸>心磷脂>磷脂酰胆碱>磷脂酰甘油约为磷脂酰乙醇胺>磷脂酸约为磷脂酰丝氨酸> N-酰基磷脂酰乙醇胺>甘油二酯。因此，膜结合的α-突触核蛋白在双层的界面区域结合，在那里它可能有利于某些磷脂的局部浓度。
Alpha-synuclein is a small presynaptic protein, which is linked to the development of Parkinson's disease. Alpha-synuclein partitions between cytosolic and vesicle-bound states, where membrane binding is accompanied by the formation of an amphipathic helix in the N-terminal section of the otherwise unstructured protein. The impact on alpha-synuclein of binding to vesicle-like liposomes has been studied extensively, but far less is known about the impact of alpha-synuclein on the membrane. The interactions of alpha-synuclein with phosphatidylglycerol membranes are studied here by using spin-labeled lipid species and electron spin resonance (ESR) spectroscopy to allow a detailed analysis of the effect on the membrane lipids. Membrane association of alpha-synuclein perturbs the ESR spectra of spin-labeled lipids in bilayers of phosphatidylglycerol but not of phosphatidylcholine. The interaction is inhibited at high ionic strength. The segmental motion is hindered at all positions of spin labeling in the phosphatidylglycerol sn-2 chain, while still preserving the chain flexibility gradient characteristic of fluid phospholipid membranes. Direct motional restriction of the lipid chains, resulting from penetration of the protein into the hydrophobic interior of the membrane, is not observed. Saturation occurs at a protein/lipid ratio corresponding to approximately 36 lipids/protein added. Alpha-synuclein exhibits a selectivity of interaction with different phospholipid spin labels when bound to phosphatidylglycerol membranes in the following order: stearic acid > cardiolipin > phosphatidylcholine > phosphatidylglycerol approximately phosphatidylethanolamine > phosphatidic acid approximately phosphatidylserine > N-acyl phosphatidylethanolamine > diglyceride. Accordingly, membrane-bound alpha-synuclein associates at the interfacial region of the bilayer where it may favor a local concentration of certain phospholipids.