Comparisons with amyloid-β reveal an aspartate residue that stabilizes fibrils of the aortic amyloid peptide medin.
Comparisons with amyloid-β reveal an aspartate residue that stabilizes fibrils of the aortic amyloid peptide medin.
复制标题
DOI：
10.1074/jbc.m114.602177
复制
发表时间：
2015-03-20
期刊：
影响因子：
--
通讯作者：
Middleton DA
中科院分区：
文献类型：
--
作者：
Davies HA;Madine J;Middleton DA
背景：50-aa蛋白medin的聚集体是主动脉内侧淀粉样蛋白的主要成分。结果：Medin聚集涉及与Alzheimer Aβ肽的Asp 23类似的天冬氨酸残基。结论：Medin和Aβ的聚集特性具有显著的相似性。意义：机制的见解将有助于未来的研究medin在最常见的人类淀粉样蛋白的形式。主动脉内侧淀粉样蛋白（AMA）是最常见的局部人类淀粉样蛋白，发生在几乎所有50岁以上的高加索人群中。AMA的主要蛋白质组分medin在体外容易组装成淀粉样原纤维。尽管AMA的流行，很少有人知道medin的自组装机制或原纤维的分子结构。medin的氨基酸序列与阿尔茨海默病（AD）淀粉样蛋白-β（Aβ）多肽在Aβ结构转折区周围的序列惊人相似，其中已鉴定出与家族性早发性AD相关的突变。Medin的Asp 25和Lys 30与Aβ的残基Asp 23和Lys 28对齐，已知其在某些原纤维形态中形成稳定盐桥。在这里，我们表明，取代天冬酰胺（D25 N）的天冬氨酸25的medin阻碍组装成原纤维和稳定的非细胞毒性寡聚体。相比之下，野生型medin在50小时内聚集成富含β-片层的淀粉样纤维。通过固态NMR对野生型原纤维进行的结构分析表明，分子重复单元包含至少两个延伸的β链，所述延伸的β链由Asp 25-Lys 30盐桥稳定的转角分开。我们认为Asp 25通过稳定肽的纤维状构象来驱动medin的组装，从而使人联想到Asp 23对Aβ聚集的影响。野生型medin和D25 N的药理学比较将有助于确定这种知之甚少的蛋白质的病理学意义。
Background: Aggregates of the 50-aa protein medin are the main constituent of aortic medial amyloid. Results: Medin aggregation involves an aspartate residue analogous to Asp23 of the Alzheimer Aβ peptide. Conclusion: There are striking similarities in the aggregation properties of medin and Aβ. Significance: Mechanistic insights will assist future investigations of medin in the most common form of human amyloid. Aortic medial amyloid (AMA) is the most common localized human amyloid, occurring in virtually all of the Caucasian population over the age of 50. The main protein component of AMA, medin, readily assembles into amyloid-like fibrils in vitro. Despite the prevalence of AMA, little is known about the self-assembly mechanism of medin or the molecular architecture of the fibrils. The amino acid sequence of medin is strikingly similar to the sequence of the Alzheimer disease (AD) amyloid-β (Aβ) polypeptides around the structural turn region of Aβ, where mutations associated with familial, early onset AD, have been identified. Asp25 and Lys30 of medin align with residues Asp23 and Lys28 of Aβ, which are known to form a stabilizing salt bridge in some fibril morphologies. Here we show that substituting Asp25 of medin with asparagine (D25N) impedes assembly into fibrils and stabilizes non-cytotoxic oligomers. Wild-type medin, by contrast, aggregates into β-sheet-rich amyloid-like fibrils within 50 h. A structural analysis of wild-type fibrils by solid-state NMR suggests a molecular repeat unit comprising at least two extended β-strands, separated by a turn stabilized by a Asp25-Lys30 salt bridge. We propose that Asp25 drives the assembly of medin by stabilizing the fibrillar conformation of the peptide and is thus reminiscent of the influence of Asp23 on the aggregation of Aβ. Pharmacological comparisons of wild-type medin and D25N will help to ascertain the pathological significance of this poorly understood protein.