J Mol Biol. 2019 May 3;431(10):1920-1939. doi: 10.1016/j.jmb.2019.03.022. Epub 2019 Mar 28.
The M13 tip protein, g3p, binds the C-terminal domain of the bacterial membrane protein TolA via β-sheet augmentation, facilitating viral entry into Escherichia coli. G3p binding leads to rearrangement of the β strands and partial unfolding of TolA. G3p also binds multiple amyloid assemblies with high affinity, and it can remodel them into amorphous aggregates. We previously showed that amyloid binding activity is defined by the two g3p N-terminal domains, which we call the general amyloid interaction motif (GAIM). GAIM-hIgG1Fc fusions, which add immune effector function to amyloid targeting of GAIM, mediate reduction of two CNS amyloid deposits, Aβ plaques and tau tangles, in transgenic animal models of neurodegenerative disease. We carried out site-directed mutagenesis of GAIM to identify variants with altered amyloid binding and remodeling activity. A small set of residues along the inner strands of the two domains regulates both activities. The specificity of amyloid binding is governed by individual domain stability and inter-domain interactions. Our studies reveal several lines of similarity between GAIM binding to amyloids and g3p binding to its E. coli membrane target, TolA. Based on these studies, we designed new GAIM fusions that show enhanced binding potency towards multiple amyloid aggregates.
M13 尖端蛋白 g3p 通过β-折叠增加与细菌膜蛋白 TolA 的 C 末端结构域结合，促进病毒进入大肠杆菌。G3p 结合导致β链的重排和 TolA 的部分展开。G3p 还能与多种淀粉样蛋白聚集物高亲和力结合，并能将其重塑为无定形聚集体。我们之前表明，淀粉样蛋白结合活性由 g3p 的两个 N 末端结构域定义，我们称之为通用淀粉样蛋白相互作用基序（GAIM）。GAIM-hIgG1Fc 融合物为 GAIM 的淀粉样蛋白靶向增加了免疫效应功能，介导减少神经退行性疾病转基因动物模型中两种中枢神经系统淀粉样沉积物，即 Aβ 斑块和 tau 缠结。我们对 GAIM 进行了定点突变，以鉴定具有改变的淀粉样蛋白结合和重塑活性的变体。两个结构域的内链上的一小部分残基调节这两种活性。淀粉样蛋白结合的特异性由单个结构域稳定性和结构域间相互作用决定。我们的研究揭示了 GAIM 与淀粉样蛋白结合和 g3p 与其大肠杆菌膜靶标 TolA 结合之间的几条相似性。基于这些研究，我们设计了新的 GAIM 融合物，它们显示出对多种淀粉样蛋白聚集物的增强结合效力。
