Conformational Changes and Membrane Interaction of the Bacterial Phospholipase, ExoU: Characterization by Site-Directed Spin Labeling
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Numerous pathogenic bacteria produce proteins evolved to facilitate their survival and dissemination by modifying the host environment. These proteins, termed effectors, often play a significant role in determining the virulence of the infection. Consequently, bacterial effectors constitute an important class of targets for the development of novel antibiotics. ExoU is a potent phospholipase effector produced by the opportunistic pathogen Pseudomonas aeruginosa. Previous studies have established that the phospholipase activity of ExoU requires non-covalent interaction with ubiquitin, however the molecular details of the mechanism of activation and the manner in which ExoU associates with a target lipid bilayer are not understood. In this review we describe our recent studies using site-directed spin labeling (SDSL) and EPR spectroscopy to elucidate the conformational changes and membrane interactions that accompany activation of ExoU. We find that ubiquitin binding and membrane interaction act synergistically to produce structural transitions that occur upon ExoU activation, and that the C-terminal four-helix bundle of ExoU functions as a phospholipid-binding domain, facilitating the association of ExoU with the membrane surface.
KeywordsPhospholipase EPR Spin labeling ExoU Pseudomonas aeruginosa
This work is supported by National Institutes of Health grants GM114234 (J.B.F.) and AI104922 (D.W.F.). DEER instrumentation was supported by NIH grants S10RR022422 and S10OD011937.
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Conflict of Interest
The authors declare that they have no conflicts of interest with the contents of this article. The contentis solely the responsibility of the authors and does not necessarily represent the official views of the NationalInstitutes of Health.
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