Bisaglia Marco, Tessari Isabella, Pinato Luca, Bellanda Massimo, Giraudo Sabrina, Fasano Mauro, Bergantino Elisabetta, Bubacco Luigi, Mammi Stefano
Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy.
Biochemistry. 2005 Jan 11;44(1):329-39. doi: 10.1021/bi048448q.
Human alpha-synuclein is a 140-amino acid protein of unknown function abundantly expressed in the brain and found in Lewy bodies, a characteristic feature of Parkinson's disease. Alpha-synuclein is random in water under physiological conditions, but the first approximately 100 residues interact with SDS micelles or acidic phospholipid small unilamellar vesicles and adopt an ordered conformation. The rest of the molecule remains disordered in the bulk of the solution. The conformation of the N-terminal portion of the molecule in lipids was described as an extended helix [Ramakrishnan, M., Jensen, P. H., and Marsh, D. (2003) Biochemistry 42, 12919-12926], as two distinct alpha-helices interrupted by a two-residue break [Chandra, S., Chen, X., Rizo, J., Jahn, R., and Sudhof, T. C. (2003) J. Biol. Chem. 278, 15313-15318], or as a noncanonical conformation, the alpha11/3 helix [Bussell, R., Jr., and Eliezer, D. (2003) J. Mol. Biol. 329, 763-778]. We characterized the topology of the different regions of alpha-synuclein relative to the surface of SDS micelles using spin probe-induced broadening of NMR signals, (15)N relaxation measurements, and fluorescence spectroscopy. Our results support the presence of two N-terminal helices, positioned on the surface of the micelle and separated by a flexible stretch. The region of residues 61-95 of the protein also adopts a helical conformation, but it is partially embedded in the micelle. These results could shed some light on the role of the membrane on the aggregation process of alpha-synuclein.
人α-突触核蛋白是一种由140个氨基酸组成的蛋白质，功能未知，在大脑中大量表达，并存在于路易小体中，这是帕金森病的一个特征性表现。在生理条件下，α-突触核蛋白在水中呈无规状态，但最初大约100个残基会与十二烷基硫酸钠（SDS）胶束或酸性磷脂小单层囊泡相互作用，并呈现出有序构象。分子的其余部分在溶液主体中仍保持无序状态。脂质中该分子N端部分的构象被描述为延伸螺旋[拉马克里什南，M.，詹森，P. H.，和马什，D.（2003年）《生物化学》42卷，12919 - 12926页]，为两个由两个残基间断开的不同α-螺旋[钱德拉，S.，陈，X.，里佐，J.，扬，R.，和苏多霍夫，T. C.（2003年）《生物化学杂志》278卷，15313 - 15318页]，或为一种非经典构象，即α11/3螺旋[小布塞尔，R.，和埃利泽，D.（2003年）《分子生物学杂志》329卷，763 - 778页]。我们利用自旋探针诱导的核磁共振信号展宽、（15）N弛豫测量和荧光光谱法，表征了α-突触核蛋白不同区域相对于SDS胶束表面的拓扑结构。我们的结果支持存在两个位于胶束表面且由一段柔性片段隔开的N端螺旋。该蛋白质61 - 95位残基区域也呈现螺旋构象，但部分嵌入胶束中。这些结果可能有助于阐明膜在α-突触核蛋白聚集过程中的作用。
