Eosinophil Cationic Protein High-Affinity Binding to Bacteria-Wall Lipopolysaccharides and Peptidoglycans
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- 作者：Marc Torrent ; Susanna Navarro ; Mohammed Moussaoui ; M. Victò ; ria Nogué ; s ; Ester Boix
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：March 18, 2008
- 年：2008
- 卷：47
- 期：11
- 页码：3544 - 3555
- 全文大小：670K
- 年卷期：v.47,no.11(March 18, 2008)
- ISSN：1520-4995
文摘
The eosinophil cationic protein (ECP) is an eosinophil-secreted RNase involved in the immune host defense, with a cytotoxic activity against a wide range of pathogens. The protein displays antimicrobial activity against both Gram-negative and Gram-positive strains. The protein can destabilize lipid bilayers, although the action at the membrane level can only partially account for its bactericidal activity. We have now shown that ECP can bind with high affinity to the bacteria-wall components. We have analyzed its specific association to lipopolysaccharides (LPSs), its lipid A component, and peptidoglycans (PGNs). ECP high-affinity binding capacity to LPSs and lipid A has been analyzed by a fluorescent displacement assay, and the corresponding dissociation constants were calculated using the protein labeled with a fluorophor. The protein also binds in vivo to bacteria cells. Ultrastructural analysis of cell bacteria wall and morphology have been visualized by scanning and transmission electron microscopy in both Escherichia coli and Staphylococcus aureus strains. The protein damages the bacteria surface and induces the cell population aggregation on E. coli cultures. Although both bacteria strain cells retain their shape and no cell lysis is patent, the protein can induce in E. coli the outer membrane detachment. ECP also activates the cytoplasmic membrane depolarization in both strains. Moreover, the depolarization activity on E. coli does not require any pretreatment to overcome the outer membrane barrier. The protein binding to the bacteria-wall surface would represent a first encounter step key in its antimicrobial mechanism of action.