Consequences of poly-glutamine repeat length for the conformation and folding of the androgen receptor amino-terminal domain
Consequences of poly-glutamine repeat length for the conformation and folding of the androgen receptor amino-terminal domain
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DOI：
10.1677/jme-08-0042
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发表时间：
2008-11-01
影响因子：
3.5
通讯作者：
McEwan, Iain J.
中科院分区：
文献类型：
--
作者：
Davies, Philippa;Watt, Kate;McEwan, Iain J.
聚氨基酸重复序列，尤其是长链谷氨酰胺 (Q)，是转录因子和细胞信号蛋白的共同特征，并且易于扩展，导致神经退行性疾病。雄激素受体 (AR-NTD) 的氨基末端结构域具有 9 至 36 个残基之间的聚 Q 重复，当其扩展超过 40 个残基时，会导致脊髓延髓肌萎缩。我们使用光谱学和生化分析来研究扩增重复序列 (Q45) 或删除重复序列 (Delta Q) 对 AR-NTD 折叠的结构影响。圆二色光谱表明，在水溶液中，AR-NTD具有相对有限的稳定二级结构。 Poly-Q重复序列的扩展导致α螺旋结构适度增加，而重复序列的删除导致α螺旋结构的少量损失。在结构促进溶剂三氟乙醇或天然渗透剂三甲胺 N-氧化物存在下，这些效果更加明显。荧光光谱显示，Q 片段删除后，四个色氨酸残基的微环境也发生了改变。在有限的蛋白水解后，观察到 AR-NTDQ45 多肽的其他结构变化；此外，该多肽不仅表现出与疏水性探针8-苯胺萘-1-磺酸的结合增强，而且对尿素诱导的去折叠更加敏感。总而言之，这些发现支持这样的观点：poly-Q 重复序列的存在和长度调节 AR-NTD 的折叠和结构。
Poly-amino acid repeats, especially long stretches of glutamine (Q), are common features of transcription factors and cell-signalling proteins and are prone to expansion, resulting in neurodegenerative diseases. The amino-terminal domain of the androgen receptor (AR-NTD) has a poly-Q repeat between 9 and 36 residues, which when it expands above 40 residues results in spinal bulbar muscular atrophy. We have used spectroscopy and biochemical analysis to investigate the structural consequences of an expanded repeat (Q45) or removal of the repeat (Delta Q) on the folding of the AR-NTD. Circular dichroism spectroscopy revealed that in aqueous solution, the AR-NTD has a relatively limited amount of stable secondary structure. Expansion of the poly-Q repeat resulted in a modest increase in a-helix structure, while deletion of the repeat resulted in a small loss of a-helix structure. These effects were more pronounced in the presence of the structure-promoting solvent trifluoroethanol or the natural osmolyte trimethylamine N-oxide. Fluorescence spectroscopy showed that the microenvironments of four tryptophan residues were also altered after the deletion of the Q stretch. Other structural changes were observed for the AR-NTDQ45 polypeptide after limited proteolysis; in addition, this polypeptide not only showed enhanced binding of the hydrophobic probe 8-anilinonaphthalene-1-sulphonic acid but was more sensitive to urea-induced unfolding. Taken together, these findings support the view that the presence and length of the poly-Q repeat modulate the folding and structure of the AR-NTD.