Masino Laura, Musi Valeria, Menon Rajesh P, Fusi Paola, Kelly Geoff, Frenkiel Thomas A, Trottier Yvon, Pastore Annalisa
National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK.
FEBS Lett. 2003 Aug 14;549(1-3):21-5. doi: 10.1016/s0014-5793(03)00748-8.
Anomalous expansion of a polyglutamine (polyQ) tract in the protein ataxin-3 causes spinocerebellar ataxia type 3, an autosomal dominant neurodegenerative disease. Very little is known about the structure and the function of ataxin-3, although this information would undoubtedly help to understand why the expanded protein forms insoluble nuclear aggregates and causes neuronal cell death. With the aim of establishing the domain architecture of ataxin-3 and the role of the polyQ tract within the protein context, we have studied the human and murine orthologues using a combination of techniques, which range from limited proteolysis to circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies. The two protein sequences share a highly conserved N-terminus and differ only in the length of the glutamine repeats and in the C-terminus. Our data conclusively indicate that ataxin-3 is composed by a structured N-terminal domain, followed by a flexible tail. Moreover, [(15)N]glutamine selectively labelled samples allowed us to have a direct insight by NMR into the structure of the polyQ region.
ataxin-3蛋白中多聚谷氨酰胺（polyQ）序列的异常扩展会导致3型脊髓小脑共济失调，这是一种常染色体显性神经退行性疾病。尽管ataxin-3的结构和功能信息无疑有助于理解为何扩展后的蛋白会形成不溶性核聚集体并导致神经元细胞死亡，但目前我们对其知之甚少。为了确定ataxin-3的结构域架构以及polyQ序列在蛋白整体中的作用，我们结合了多种技术对人和小鼠的同源蛋白进行了研究，这些技术包括有限蛋白酶解、圆二色性（CD）光谱和核磁共振（NMR）光谱。这两种蛋白序列在N端高度保守，仅在谷氨酰胺重复序列的长度和C端有所不同。我们的数据确凿地表明，ataxin-3由一个结构化的N端结构域和一个柔性尾部组成。此外，[(15)N]谷氨酰胺选择性标记的样品使我们能够通过核磁共振直接深入了解polyQ区域的结构。
