Departament de Bioquimica i Biologia Molecular, Facultat de Biociencies, Universitat Autonoma de Barcelona, 08193-Bellaterra, Spain.
Biomacromolecules. 2010 Aug 9;11(8):1983-90. doi: 10.1021/bm100334u.
Eosinophil cationic protein (ECP) is an antimicrobial protein belonging to the superfamily of RNase A. ECP exhibits a broad spectrum of action against bacteria and, at higher concentrations, displays cytotoxic activity to eukaryotic cells. Recently, a powerful aggregation activity for lipid vesicles and for the gram-negative E. coli specie has also been related to the protein toxicity. Here we present the amyloid-like aggregation capacity of ECP. This is the first report of amyloid aggregation in a native nonengineered ribonuclease. The ECP aggregates are able to bind the amyloid-diagnostic dyes Thioflavin T and Congo Red and display a protofibril morphology when observed under electronic microscopy. We have also identified an N-terminus hydrophobic patch (residues 8-16) that is required for the amyloid aggregation process. A single substitution, I13A, breaks the aggregation prone sequence and abolishes the amyloid aggregation ability. Moreover, the corresponding R1N19 peptide is able to reproduce the protein amyloid-like aggregation behavior. The results may provide new clues on the protein antimicrobial mechanism and its toxicity to the host tissues in inflammation processes.
嗜酸性粒细胞阳离子蛋白（ECP）是一种属于 RNase A 超家族的抗菌蛋白。ECP 对细菌具有广谱作用，在较高浓度下对真核细胞显示细胞毒性。最近，该蛋白的脂质体聚集活性和针对革兰氏阴性大肠杆菌物种的活性也与蛋白毒性有关。在这里，我们提出了 ECP 的类淀粉样聚集能力。这是第一个在天然非工程核糖核酸酶中报告的淀粉样聚集。ECP 聚集体能够结合淀粉样诊断染料硫黄素 T 和刚果红，并在电子显微镜下观察时呈现原纤维形态。我们还鉴定了一个 N 端疏水区（残基 8-16），该区域是淀粉样聚集过程所必需的。单一取代 I13A 破坏了易于聚集的序列并消除了淀粉样聚集能力。此外，相应的 R1N19 肽能够再现蛋白的类淀粉样聚集行为。这些结果可能为蛋白的抗菌机制及其在炎症过程中对宿主组织的毒性提供新的线索。
