title: Eosinophil cationic protein aggregation: identification of an N-terminus amyloid prone region.
abstract: 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.
authors.affiliation: Departament de Bioquimica i Biologia Molecular, Facultat de Biociencies, Universitat Autonoma de Barcelona, 08193-Bellaterra, Spain. marc.torrent@uab.cat
authors.forename: Marc
authors.initials: M
authors.lastname: Torrent
authors.forename: Francesco
authors.initials: F
authors.lastname: Odorizzi
authors.forename: M Victòria
authors.initials: MV
authors.lastname: Nogués
authors.forename: Ester
authors.initials: E
authors.lastname: Boix
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D002942:Circular Dichroism; D047150:Eosinophil Cationic Protein / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000682:Amyloid; D047150:Eosinophil Cationic Protein