Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico.
Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Ciudad de México, Mexico.
FEBS J. 2017 Nov;284(21):3702-3717. doi: 10.1111/febs.14265. Epub 2017 Oct 12.
Light chain amyloidosis is a lethal disease where vital organs are damaged by the fibrillar aggregation of monoclonal light chains. λ6a is an immunoglobulin light chain encoded by the germ-line gene segment implicated in this disease. AR is a patient-derived germ-line variant with a markedly low thermodynamic stability and prone to form fibrils in vitro in less than an hour. Here, we sought to stabilize this domain by mutating some residues back to the germ-line sequence, and the most stabilizing mutations were the single-mutant AR-F21I and the double-mutant AR-F21/IV104L, both located in the hydrophobic core. While mutation Arg25Gly in 6aJL2 destabilized the domain, mutating Gly25 back to arginine in AR did not contribute to stabilization as expected. Crystallographic structures of AR and 6a-R25G were generated to explain this discrepancy. Finally, 6a-R25G crystals revealed an octameric assembly which was emulated into 6aJL2 and AR crystals by replicating their structural parameters and suggesting a common assembly pattern.
The atomic coordinates and structure factors have been deposited in the Protein Data Bank under the accession numbers 5IR3 and 5C9K.
轻链淀粉样变性是一种致命疾病，单克隆轻链的纤维状聚集会损害重要器官。λ6a 是一种免疫球蛋白轻链，由涉及该疾病的 germ-line 基因片段编码。AR 是一种源自患者的 germ-line 变体，其热力学稳定性明显较低，在不到一个小时的时间内容易在体外形成纤维。在这里，我们试图通过将一些残基突变回 germ-line 序列来稳定这个结构域，最稳定的突变是位于疏水核心的单突变体 AR-F21I 和双突变体 AR-F21/IV104L。虽然突变 Arg25Gly 在 6aJL2 中使结构域不稳定，但如预期的那样，将 AR 中的 Gly25 突变为精氨酸并没有有助于稳定。生成了 AR 和 6a-R25G 的晶体结构来解释这种差异。最后，6a-R25G 晶体揭示了一个八聚体组装体，通过复制其结构参数并暗示一种常见的组装模式，将其模拟到 6aJL2 和 AR 晶体中。
原子坐标和结构因子已在蛋白质数据库中以 5IR3 和 5C9K 的条目号存储。
