Proteomic analysis of egg white heparin-binding proteins: towards the identification of natural antibacterial molecules

The chicken egg resists most environmental microbes suggesting that it potentially contains efficient antimicrobial molecules. Considering that some heparin-binding proteins in mammals are antibacterial, we investigated the presence and the antimicrobial activity of heparin-binding proteins from chicken egg white. Mass spectrometry analysis of the proteins recovered after heparin-affinity chromatography, revealed 20 proteins, including known antimicrobial proteins (avidin, lysozyme, TENP, ovalbumin-related protein X and avian bêta-defensin 11). The antibacterial activity of three new egg candidates (vitelline membrane outer layer protein 1, beta-microseminoprotein-like (LOC101750704) and pleiotrophin) was demonstrated against Listeria monocytogenes and/or Salmonella enterica Enteritidis. We showed that all these molecules share the property to inhibit bacterial growth through their heparin-binding domains. However, vitelline membrane outer layer 1 has additional specific structural features that can contribute to its antimicrobial potential. Moreover, we identified potential supplementary effectors of innate immunity including mucin 5B, E-selectin ligand 1, whey acidic protein 3, peptidyl prolyl isomerase B and retinoic acid receptor responder protein 2. These data support the concept of using heparin affinity combined to mass spectrometry to obtain an overview of the various effectors of innate immunity composing biological milieus, and to identify novel antimicrobial candidates of interest in the race for alternatives to antibiotics.