AMYLOID FIBRIL FORMATION REQUIRES A CHEMICALLY DISCRIMINATING NUCLEATION EVENT - STUDIES OF AN AMYLOIDOGENIC SEQUENCE FROM THE BACTERIAL PROTEIN OSMB
AMYLOID FIBRIL FORMATION REQUIRES A CHEMICALLY DISCRIMINATING NUCLEATION EVENT - STUDIES OF AN AMYLOIDOGENIC SEQUENCE FROM THE BACTERIAL PROTEIN OSMB
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DOI：
10.1021/bi00164a008
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发表时间：
1992-12-15
期刊：
影响因子：
2.9
通讯作者：
LANSBURY, PT
中科院分区：
文献类型：
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作者：
JARRETT, JT;LANSBURY, PT
大肠杆菌OsmB蛋白的序列被发现类似于阿尔茨海默氏病的β淀粉样蛋白的C-末端区域，这似乎是其不寻常的结构和溶解度特性的主要决定因素。合成了OsmB蛋白28-44位残基的多肽，并分析了其构象特性和聚集行为。肽OsmB（28-44）显示出形成淀粉样原纤维，设计用于测试原纤维形成的序列特异性的两个序列类似物也是如此。这些原纤维结合刚果红，其中两种肽显示双折射。通过电子显微镜和傅立叶变换红外光谱分析肽原纤维。观察到在分子水平上无法解释的细微差异。通过监测过饱和水溶液的浊度来跟踪每种肽的原纤维形成速率。聚集的动力学的特征在于由延迟期，在此期间的溶液保持清晰，随后由成核事件，导致生长阶段，在此期间的溶液变得粘稠和浑浊，由于不溶性原纤维的存在。聚集动力学障碍的观察是结晶事件的典型特征。延迟期可以通过用先前形成的原纤维接种过饱和溶液来消除。每种肽都可以通过由相同肽形成的原纤维成核，但不能通过来自密切相关序列的原纤维成核，这表明原纤维生长需要特定的疏水相互作用。似乎很可能是这种重复的序列基序，包括大部分的OsmB蛋白质序列，决定了该蛋白质的结构和可能的功能。虽然淀粉样蛋白的形成不需要这个序列，但OsmB和β淀粉样蛋白之间的序列和组成的相似性可能是显着的。此外，这些研究表明，淀粉样蛋白原纤维的形成是化学歧视，原纤维形成的成核是淀粉样蛋白生成的限速步骤。这一发现对于理解阿尔茨海默病中淀粉样蛋白的形成具有重要的意义。
The sequence of the Escherichia coli OsmB protein was found to resemble that of the C-terminal region of the beta amyloid protein of Alzheimers's disease, which seems to be the major determinant of its unusual structural and solubility properties. A peptide corresponding to residues 28-44 of the OsmB protein was synthesized, and its conformational properties and aggregation behavior were analyzed. The peptide OsmB(28-44) was shown to form amyloid fibrils, as did two sequence analogs designed to test the sequence specificity of fibril formation. These fibrils bound Congo red, and two of the peptides showed birefringence. The peptide fibrils were analyzed by electron microscopy and Fourier transform infrared spectroscopy. Subtle differences were observed which were not interpretable at the molecular level. The rate of fibril formation by each peptide was followed by monitoring the turbidity of supersaturated aqueous solutions. The kinetics of aggregation were characterized by a delay period during which the solution remained clear, followed by a nucleation event which led to a growth phase, during which the solution became viscous and turbid due to the presence of insoluble fibrils. The observation of a kinetic barrier to aggregation is typical of a crystallization event. The delay period could be eliminated by seeding the supersaturated solution with previously formed fibrils. Each peptide could be nucleated by fibrils formed from that same peptide, but not by fibrils from closely related sequences, suggesting that fibril growth requires specific hydrophobic interactions. It appears likely that this repeated sequence motif which comprises most of the OsmB protein sequence, dictates the structure and possibly the function of that protein. While amyloid formation was shown not to require this sequence, similarities in sequence and composition between OsmB and the beta amyloid protein may be significant. Furthermore, these studies demonstrate that amyloid fibril formation is chemically discriminating, and that nucleation of fibril formation is the rate-limiting step in amyloidogenesis. This finding has important ramifications for the understanding of amyloid formation in Alzheimer's disease.