Khurana Ritu, Souillac Pierre O, Coats Alisa C, Minert Lauren, Ionescu-Zanetti Cristian, Carter Sue A, Solomon Alan, Fink Anthony L
Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
Amyloid. 2003 Jun;10(2):97-109. doi: 10.3109/13506120309041731.
In an attempt to understand the mechanism of amyloid fibril formation in light chain amyloidosis, the properties of amyloidogenic (SMA) and benign (LEN) immunoglobulin light chain variable domains (VL) were compared. The conformations of LEN and SMA were measured using secondary and tertiary structural probes over the pH range from 2 and 8. At all pH values, LEN was more stable than SMA. The CD spectra of LEN at pH 2 were comparable to those of SMA at pH 7.5, indicating that the low pH conformation of LEN closely resembles that of SMA at physiological pH. At low pH, a relatively unfolded intermediate conformation is populated for SMA and rapidly leads to amyloid fibrils. The lack of such an intermediate with LEN, is attributed to sequence differences and accounts for the lack of LEN fibrils in the absence of agitation. A kappa IV-specific monoclonal antibody that recognizes the N-terminal of SMA caused unraveling of the fibrils to the protofilaments and was observed to bind to one end of SMA protofilaments by atomic force microscopy. The antibody result indicates that each protofilament is asymmetric with different ends. A model for the formation of fibrils by SMA is proposed.
为了了解轻链淀粉样变性中淀粉样纤维形成的机制，对淀粉样变性（SMA）和良性（LEN）免疫球蛋白轻链可变区（VL）的特性进行了比较。使用二级和三级结构探针在pH值2至8范围内测量了LEN和SMA的构象。在所有pH值下，LEN比SMA更稳定。LEN在pH 2时的圆二色光谱与SMA在pH 7.5时的光谱相当，表明LEN在低pH下的构象与SMA在生理pH下的构象非常相似。在低pH下，SMA会形成相对未折叠的中间构象，并迅速导致淀粉样纤维的形成。LEN缺乏这种中间构象，这归因于序列差异，并解释了在没有搅拌的情况下LEN纤维缺乏的原因。一种识别SMA N端的κIV特异性单克隆抗体导致纤维解聚为原丝，并通过原子力显微镜观察到它与SMA原丝的一端结合。抗体结果表明每个原丝是不对称的，两端不同。提出了SMA形成纤维的模型。
