A partially structured species of β2-microglobulin is significantly populated under physiological conditions and involved in fibrillogenesis
A partially structured species of β2-microglobulin is significantly populated under physiological conditions and involved in fibrillogenesis
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DOI：
10.1074/jbc.m107040200
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发表时间：
2001-12-14
影响因子：
4.8
通讯作者：
Bellotti, V
中科院分区：
文献类型：
--
作者：
Chiti, F;De Lorenzi, E;Bellotti, V
β（2）-微球蛋白（β（2）-M）是透析相关性淀粉样变性中形成淀粉样沉积物的蛋白质，其折叠涉及形成称为I-2的部分折叠构象，其缓慢转化为天然折叠N。在这里，我们表明，部分折叠的物种I-2可以通过毛细管电泳从N中分离。用该技术获得的数据和用固有荧光获得的动力学数据的分析表明，在接近生理的pH和温度条件下，I-2构象在平衡时被填充至类似于14 +/- 8%。在从患者中提取的原纤维的存在下，I-2构象异构体具有比N高5倍的聚集倾向，如硫代黄素T检验和光散射测量所示。从这些结果中提出了β（2）-M在体内聚集的机制，涉及预先形成的原纤维与平衡时存在的I-2部分的缔合。分离和定量参与淀粉样蛋白生成过程的β 2-M部分折叠构象异构体的可能性为监测旨在从循环β 2-M池中减少此类物质的血液透析程序提供了新的机会，也为设计将此类物质视为推定分子靶点的新药物方法提供了新的机会。
The folding Of beta (2)-microglobulin (beta (2)-M), the protein forming amyloid deposits in dialysis-related amyloidosis, involves formation of a partially folded conformation named I-2, which slowly converts into the native fold, N. Here we show that the partially folded species I-2 can be separated from N by capillary electrophoresis. Data obtained with this technique and analysis of kinetic data obtained with intrinsic fluorescence indicate that the I-2 conformation is populated to similar to 14 +/- 8% at equilibrium under conditions of pH and temperature close to physiological. In the presence of fibrils extracted from patients, the I-2 conformer has a 5-fold higher propensity to aggregate than N, as indicated by the thioflavine T test and light scattering measurements. A mechanism of aggregation of beta (2)-M in vivo involving the association of the preformed fibrils with the fraction of I-2, existing at equilibrium is proposed from these results. The possibility of isolating and quantifying a partially folded conformer of beta (2)-M involved in the amyloidogenesis process provides new opportunities to monitor hemodialytic procedures aimed at the reduction of such species from the pool of circulating beta (2)-m but also to design new pharmaceutical approaches that consider such species as a putative molecular target.