Towards a new approach for class II bacteriocins: using suicide probes to study their mechanism of action

RÍOS COLOMBO NS; CHALÓN MC; DUPUY FG; BELLOMIO A

Lima

Workshop; Biophysical Society Thematic Meetings; 2019

Biophysical Society

The study of alternative antimicrobials has become relevant in the last years because of theincreasing resistance to common antibiotics. Class II bacteriocins are unmodified membraneactivepeptides that act over a narrow spectrum of bacterial targets. They are believed to bind aspecific 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 porestructure involves the specific receptor. 2) Study the effect three bacteriocins in some membraneproperties using fluorescent spectroscopy. Methods: we designed chimeric peptides fusing thebitopic membrane protein EtpM with different class II bacteriocins: enterocin CRL35, pediocinPA-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 anexpression host because this bacterium is naturally insensitive to enterocin and pediocin, sincetheir specific receptor Man-PTS is not present on its inner membrane. In addition, an sdaCmutant E. coli strain was employed as a receptor-free host for MccV, as it does not expressSdaC, the specific membrane receptor for this microcin. The effect of these suicide probes intransmembrane 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 ismore likeable to act as docking molecule and it could be dispensable for the final step ofmembrane disruption. These set of chimeric peptides also represent an in vivo system that allowsto study the interaction of the bacteriocins with real bacterial membranes, instead of modelmembranes. In this work we demonstrate how these peptides can depolarize or increasemembrane lipids order, even in the absence of the specific receptor.