TOWARDS A NEW APPROACH FOR CLASS II BACTERIOCINS: USING SUICIDE PROBES TO STUDY THEIR MECHANISM OF ACTION

RIOS COLOMBO, N.S.; CHALON M.C.; DUPUY, F.G.; BELLOMIO, A

Lima

Encuentro; Biophysical Society Thematic Meetings. Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level; 2019

Sociedad de Biofisica.

The study of alternative antimicrobials has become relevant in the last years because of the increasing resistance to common antibiotics. Class II bacteriocins are unmodified membrane active peptides that act over a narrow spectrum of bacterial targets. They are believed to bind a specific receptor on the membrane that would participate in the formation of a pore, leading tomembrane permeabilization and cell death. Objectives: 1) Reveal whether or not the pore structure involves the specific receptor. 2) Study the effect three bacteriocins in some membrane properties using fluorescent spectroscopy. Methods: we designed chimeric peptides fusing the bitopic membrane protein EtpM with different class II bacteriocins: enterocin CRL35, pediocin PA-1 and microcin V. These hybrid proteins EtpM-bacteriocin (also called ?suicide probes?) were heterologously expressed in E. coli and E. coli sdaC respectively. We chose E. coli as an expression host because this bacterium is naturally insensitive to enterocin and pediocin, since their specific receptor Man-PTS is not present on its inner membrane. In addition, an sdaC mutant E. coli strain was employed as a receptor-free host for MccV, as it does not express SdaC, the specific membrane receptor for this microcin. The effect of these suicide probes in transmembrane potential and membrane fluidity was also assessed. Results and conclusions: Since the suicide probes kill the expressing host cells, we suggest that the specific receptor is more likeable to act as docking molecule and it could be dispensable for the final step of membrane disruption. These set of chimeric peptides also represent an in vivo system that allows to study the interaction of the bacteriocins with real bacterial membranes, instead of modelmembranes. In this work we demonstrate how these peptides can depolarize or increase membrane lipids order, even in the absence of the specific receptor.