Novozymes A/S, Bagsvaerd, Denmark.
Technical University of Denmark, Department of Chemistry, Kgs. Lyngby, Denmark.
Nat Commun. 2022 Jun 7;13(1):3162. doi: 10.1038/s41467-022-30462-w.
Self-assembly and fibril formation play important roles in protein behaviour. Amyloid fibril formation is well-studied due to its role in neurodegenerative diseases and characterized by refolding of the protein into predominantly β-sheet form. However, much less is known about the assembly of proteins into other types of supramolecular structures. Using cryo-electron microscopy at a resolution of 1.97 Å, we show that a triple-mutant of the anti-microbial peptide plectasin, PPI42, assembles into helical non-amyloid fibrils. The in vitro anti-microbial activity was determined and shown to be enhanced compared to the wildtype. Plectasin contains a cysteine-stabilised α-helix-β-sheet structure, which remains intact upon fibril formation. Two protofilaments form a right-handed protein fibril. The fibril formation is reversible and follows sigmoidal kinetics with a pH- and concentration dependent equilibrium between soluble monomer and protein fibril. This high-resolution structure reveals that α/β proteins can natively assemble into fibrils.
自组装和纤维形成在蛋白质行为中起着重要作用。由于其在神经退行性疾病中的作用，淀粉样纤维的形成得到了很好的研究，其特征是蛋白质重新折叠成主要的β-折叠形式。然而，对于蛋白质组装成其他类型的超分子结构的了解要少得多。我们使用分辨率为 1.97Å 的冷冻电子显微镜显示，一种抗菌肽 plectasin 的三重突变体 PPI42 组装成螺旋形非淀粉样纤维。测定了其体外抗菌活性，并显示其活性比野生型增强。Plectasin 含有一个半胱氨酸稳定的α-螺旋-β-折叠结构，在纤维形成过程中保持完整。两个原纤维形成一个右手蛋白纤维。纤维形成是可逆的，遵循 S 型动力学，在可溶性单体和蛋白纤维之间存在 pH 和浓度依赖性平衡。该高分辨率结构表明，α/β 蛋白可以天然组装成纤维。
