Eight severe inherited neurodegenerative diseases are caused by expansion of glutamine repeats in the affected proteins. In every case, proteins with repeats of fewer than 38 glutamine residues are harmless, but those with repeats of more than 41 glutamine residues form toxic neuronal nuclear aggregates in the affected neurons. Similarly, proteins that have repeats of fewer than 37 glutamine residues are soluble in vitro, whereas proteins with repeats of more than 40 glutamine residues precipitate as insoluble fibres, apparently because of a structural transition associated with the increased length.

中文翻译：

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谷氨酰胺重复和神经退行性疾病：分子方面。

八种严重的遗传性神经退行性疾病是由受影响的蛋白质中谷氨酰胺重复序列的扩增引起的。在每种情况下，重复少于38个谷氨酰胺残基的蛋白质都是无害的，但是重复超过41个谷氨酰胺残基的蛋白质在受影响的神经元中形成有毒的神经元核聚集体。类似地，具有少于37个谷氨酰胺残基的重复序列的蛋白质在体外可溶，而具有超过40个谷氨酰胺残基的重复序列的蛋白质沉淀为不溶性纤维，这显然是由于与长度增加相关的结构转变。