title: Bactericidal and membrane disruption activities of the eosinophil cationic protein are largely retained in an N-terminal fragment.
abstract: ECP (eosinophil cationic protein) is an eosinophil secretion protein with antipathogen activities involved in the host immune defence system. The bactericidal capacity of ECP relies on its action on both the plasma membrane and the bacterial wall. In a search for the structural determinants of ECP antimicrobial activity, we have identified an N-terminal domain (residues 1-45) that retains most of ECP's membrane-destabilizing and antimicrobial activities. Two sections of this domain, ECP-(1-19) and ECP-(24-45), have also been evaluated. All three peptides bind and partially insert into lipid bilayers, inducing aggregation of lipid vesicles and leakage of their aqueous content. In such an environment, the peptides undergo conformational change, significantly increasing their alpha-helix content. The bactericidal activity of the three peptides against Escherichia coli and Staphylococcus aureus has been assessed at both the cytoplasmic membrane and the bacterial envelope levels. ECP-(1-45) and ECP-(24-45) partially retain the native proteins ability to bind LPS (lipopolysaccharides), and electron microscopy reveals cell damage by both peptides. Interestingly, in the E. coli cells agglutination activity of ECP is only retained by the longest segment ECP-(1-45). Comparative results suggest a task distribution, whereby residues 1-19 would contribute to membrane association and destabilization, while the 24-45 region would be essential for bactericidal action. Results also indicate that ECP cytotoxicity is not uniquely dependant on its membrane disruption capacity, and that specific interactions at the bacteria wall are also involved.
authors.affiliation: Department Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Torrent
authors.forename: Beatriz G
authors.initials: BG
authors.lastname: de la Torre
authors.forename: Victòria M
authors.initials: VM
authors.lastname: Nogués
authors.forename: David
authors.initials: D
authors.lastname: Andreu
authors.forename: Ester
authors.initials: E
authors.lastname: Boix
mesh_terms: D020816:Amino Acid Motifs; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism; D001424:Bacterial Infections / Q000378:metabolism / Q000382:microbiology; D001425:Bacterial Outer Membrane Proteins / Q000187:drug effects* / Q000378:metabolism; D047150:Eosinophil Cationic Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D047150:Eosinophil Cationic Protein; C479220:RNASE3 protein, human