In vivo systems to study class II bacteriocins toxicity and immunity

BELLOMIO, AUGUSTO; RÍOS COLOMBO, NATALIA S.; CHALÓN, MIRIAM CAROLINA

Varadero

Workshop; IUBMB/IUPAB Advanced School and Workshop on Protein-protein and membrane-protein interaction: experimental and theoretical approaches.; 2018

International Union of Biochemistry and Molecular Biology (IUBMB) / International Union of Pure and Applied Biophysics (IUPAB)

Class II bacteriocins are unmodified membrane-active peptides that act over a narrow spectrum of bacterial targets. They bind to a specific receptor on the membrane that would participate in the formation of a pore, leading to membrane permeabilization and cell death. In order to reveal whether or not the pore structure involves the specific receptor, we designed chimeric peptides fusing the membrane protein EtpM with different class II bacteriocins. We chose E. coli as a receptor-free host for the tested peptides. As the fusion EtpM-bacteriocin kills the expressing host cell, we conclude that the specific receptor would act simply as a docking molecule and it would not participate in the pore structure. An immunity protein protects the producer strain against its own bacteriocin. For antimicrobials under investigation with a view to clinical applications, the potential emergence of resistant pathogens is an issue that must be addressed. Immune mimicry, could limit the deployment of bacteriocins in clinical practice, so the study of immune mechanisms is a primary concern. The bacteriocin-immunity protein complex has never been purified or characterized in vitro. Nevertheless, this kind of interaction cannot be excluded. The EtpM-bacteriocin expressing cell acquires immunity when co-expressing the immunity protein, even in absence of the specific receptor. In this way, by using an in vivo system, we have presented sound evidence that immunity protein might bind the cognate bacteriocin, not in aqueous solution but in a membrane inserted conformation. The effect of these interactions in some membrane biophysical properties is also analyzed.