title: Human Lysozyme Peptidase Resistance Is Perturbed by the Anionic Glycolipid Biosurfactant Rhamnolipid Produced by the Opportunistic Pathogen Pseudomonas aeruginosa.
abstract: Infection by the opportunistic pathogen Pseudomonas aeruginosa (PA) is accompanied by the secretion of virulence factors such as the secondary metabolite rhamnolipid (RL) as well as an array of bacterial enzymes, including the peptidase elastase. The human immune system tries to counter this via defensive proteins such as lysozyme (HLZ). HLZ targets the bacterial cell wall but may also have other antimicrobial activities. The enzyme contains four disulfide bonds and shows high thermodynamic stability and resistance to proteolytic attack. Here we show that RL promotes HLZ degradation by several unrelated peptidases, including the PA elastase and human peptidases. This occurs although RL does not by itself denature HLZ. Nevertheless, RL binds in a sufficiently high stoichiometry (8:1 RL:HLZ) to neutralize the highly cationic surface of HLZ. The initial cleavage sites agree well with the domain boundaries of HLZ. Thus, binding of RL to native HLZ may be sufficient to allow proteolytic attack at slightly exposed sites on the protein, leading to subsequent degradation. Furthermore, biofilms of RL-producing strains of PA are protected better against high concentrations of HLZ than RL-free PA strains are. We conclude that pathogen-produced RL may weaken host defenses by facilitating degradation of key host proteins.
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Kell K
authors.initials: KK
authors.lastname: Andersen
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Vad
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Scavenius
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Enghild
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Daniel E
authors.identifier: http://orcid.org/0000-0002-2918-8989
authors.initials: DE
authors.lastname: Otzen
mesh_terms: D000838:Anions / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D018441:Biofilms; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006017:Glycolipids / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry / Q000378:metabolism*; D010196:Pancreatic Elastase / Q000378:metabolism; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D000072417:Protein Domains; D059748:Proteolysis; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D055672:Static Electricity; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D000838:Anions; D001426:Bacterial Proteins; D006017:Glycolipids; D037521:Virulence Factors; C418382:rhamnolipid; D009113:Muramidase; D010447:Peptide Hydrolases; D010196:Pancreatic Elastase