Souillac Pierre O, Uversky Vladimir N, Millett Ian S, Khurana Ritu, Doniach Sebastian, Fink Anthony L
Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
J Biol Chem. 2002 Apr 12;277(15):12666-79. doi: 10.1074/jbc.M109229200. Epub 2002 Jan 28.
Light chain amyloidosis involves the systemic pathologic deposition of monoclonal light chain variable domains of immunoglobulins as insoluble fibrils. The variable domain LEN was obtained from a patient who had no overt amyloidosis; however, LEN forms fibrils in vitro, under mildly destabilizing conditions. The in vitro kinetics of fibrillation were investigated using a wide variety of probes. The rate of fibril formation was highly dependent on the initial protein concentration. In contrast to most amyloid systems, the kinetics became slower with increasing LEN concentrations. At high protein concentrations a significant lag in time was observed between the conformational changes and the formation of fibrils, consistent with the formation of soluble off-pathway oligomeric species and a branched pathway. The presence of off-pathway species was confirmed by small angle x-ray scattering. At low protein concentrations the structural rearrangements were concurrent with fibril formation, indicating the absence of formation of the off-pathway species. The data are consistent with a model for fibrillation in which a dimeric form of LEN (at high protein concentration) inhibits fibril formation by interaction with an intermediate on the fibrillation pathway and leads to formation of the off-pathway intermediate.
轻链淀粉样变性涉及免疫球蛋白单克隆轻链可变区作为不溶性纤维的系统性病理沉积。可变区LEN取自一名无明显淀粉样变性的患者；然而，LEN在轻度不稳定条件下于体外形成纤维。使用多种探针研究了体外纤维形成动力学。纤维形成速率高度依赖于初始蛋白质浓度。与大多数淀粉样蛋白系统不同，随着LEN浓度增加，动力学变得更慢。在高蛋白浓度下，在构象变化和纤维形成之间观察到显著的时间滞后，这与可溶性非途径寡聚体物种的形成和分支途径一致。小角X射线散射证实了非途径物种的存在。在低蛋白浓度下，结构重排与纤维形成同时发生，表明未形成非途径物种。这些数据与一种纤维形成模型一致，在该模型中，LEN的二聚体形式（在高蛋白浓度下）通过与纤维形成途径上的中间体相互作用抑制纤维形成，并导致非途径中间体的形成。
