The N-Terminus of the Intrinsically Disordered Protein α-Synuclein Triggers Membrane Binding and Helix Folding
The N-Terminus of the Intrinsically Disordered Protein α-Synuclein Triggers Membrane Binding and Helix Folding
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DOI：
10.1016/j.bpj.2010.06.035
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发表时间：
2010-10-06
影响因子：
3.4
通讯作者：
Beyer, Klaus
中科院分区：
文献类型：
--
作者：
Bartels, Tim;Ahlstrom, Logan S.;Beyer, Klaus
α-突触核蛋白（α S）是一种由140个氨基酸组成的蛋白质，与许多神经退行性疾病有关。在帕金森氏病中，蛋白质通常以细胞内高分子量聚集体的形式出现。尽管aS在中枢神经系统的突触前末梢中含量丰富，但其生理功能尚不清楚。有强有力的证据表明蛋白质的膜亲和力。一种假说是脂质诱导的结合和螺旋折叠可能调节突触囊泡与突触前膜的融合以及随后的递质释放。在这里，我们表明，膜识别的N-末端是必不可少的螺旋结构域的蛋白质中的合作形成。我们使用圆二色光谱和等温滴定量热法来研究来自全长aS蛋白的不同结构域的合成肽片段。位点特异性截断和部分切割的全长蛋白质被用来进一步表征负责螺旋形成和脂质-蛋白质相互作用的结构基序。单层囊泡不同的净电荷和脂质组合物进行横向相分离或链熔融相变附近的生理温度作为模型膜。结果表明，膜诱导的螺旋折叠的前25个残基可以同时驱动静电吸引和脂质排序的变化。我们的研究结果突出了折叠成核的aS N-末端的意义，并提供了一个框架，阐明脂质诱导的蛋白质的构象转变在其细胞内环境中的作用。
Alpha-synuclein (alpha S) is a 140-amino-acid protein that is involved in a number of neurodegenerative diseases. In Parkinson's disease, the protein is typically encountered in intracellular, high-molecular-weight aggregates. Although aS is abundant in the presynaptic terminals of the central nervous system, its physiological function is still unknown. There is strong evidence for the membrane affinity of the protein. One hypothesis is that lipid-induced binding and helix folding may modulate the fusion of synaptic vesicles with the presynaptic membrane and the ensuing transmitter release. Here we show that membrane recognition of the N-terminus is essential for the cooperative formation of helical domains in the protein. We used circular dichroism spectroscopy and isothermal titration calorimetry to investigate synthetic peptide fragments from different domains of the full-length aS protein. Site-specific truncation and partial cleavage of the full-length protein were employed to further characterize the structural motifs responsible for helix formation and lipid-protein interaction. Unilamellar vesicles of varying net charge and lipid compositions undergoing lateral phase separation or chain melting phase transitions in the vicinity of physiological temperatures served as model membranes. The results suggest that the membrane-induced helical folding of the first 25 residues may be driven simultaneously by electrostatic attraction and by a change in lipid ordering. Our findings highlight the significance of the aS N-terminus for folding nucleation, and provide a framework for elucidating the role of lipid-induced conformational transitions of the protein within its intracellular milieu.