Aegerolysin RahU of the Pseudomonas aeruginosa is a bacterial protein belonging to the aegerolysin protein family (Pfam 06355), mainly composed of proteins originating from fungi and bacteria. The common property of fungal and bacterial aegerolysins is their ability to interact with membrane lipids. Some of them also possess hemolytic and toxic activity against eukaryotic cells. The RahU interacts with oxidized low-density lipoprotein, lysophosphatidylcholine and bacterial biosurfactants rhamnolipids. To elucidate the biological importance
of the interaction between aegerolysin RahU and lipids, we successfully purified single alanine substitution RahU mutants in the Escherichia coli heterologous expression system. We proved that single amino acid substitutions did not affect the structure and the stability of the RahU derivatives. With sedimentation assay and surface plasmon resonance spectrometry, we showed that RahU interacts with ceramide phosphoethanolamine, the main sphingolipid in the membranes of invertebrates. Therefore, this is the first report of a bacterial aegerolysin that interacts with the aforementioned lipid. We have also shown the binding of RahU to O-phosphorylethanolamine and the neuroendocrinic hormone noradrenaline. In addition, by using the swarming tests on Pseudomonas aeruginosa PA01, PW1205 in PW1206 strains, we suggest that aegerolysin RahU affects the swarming of Pseudomonas aeruginosa.
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