CONICET | Buscador de Institutos y Recursos Humanos

The increasing resistance to common antibiotics is highly worri-some, thus, it has led to the study of alternative antimicrobials as aprimary concern. Bacteriocins are a promising solution to this prob-lem and the understanding of their mechanism of action is funda-mental for development of new variants with potential use in thepharmaceutical industry. Class II bacteriocins are unmodified mem-brane-active peptides that act over a narrow spectrum of bacterialtargets. They are believed to bind a specific receptor on the mem-brane that would participate in the formation of a pore, leading tomembrane permeabilization and cell death. In order to reveal wheth-er or not the pore structure involves a specific receptor, we designedchimeric peptides fusing the bitopic membrane protein EtpM with dif-205ferent class II bacteriocins: enterocin CRL35 (Ent35), pediocin PA-1(PedA-1) and microcin V (MccV). We chose E. coli as an expressionhost because this bacterium is naturally insensitive to Ent35 andPedA-1, since their specific receptor Man-PTS is not present onits inner membrane. In addition, an sdaC mutant E. coli strain wasemployed as a receptor-free host for MccV, as it does not expressSdaC, the specific membrane receptor for this microcin. If the fusionEtpM-bacteriocin kills the expressing host cell, it would mean thatthe specific receptor could be dispensable for the final step of mem-brane disruption. As these constructs exert a lethal effect when theyare expressed, they are called ?suicide probes?. This hybrid proteinsEtpM-Bacteriocins were heterologeously expressed in E. coli andE. coli ΔsdaC respectively, and the results suggest that, indeed, thespecific receptor would act simply as docking molecule and it wouldnot participate in pore formation mechanisms. The effect of thesesuicide probes in some membrane properties is also analyzed