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How Many Antimicrobial Peptide Molecules Kill a Bacterium? The Case of PMAP-23
Roversi, Daniela,Luca, Vincenzo,Aureli, Simone,Park, Yoonkyung,Mangoni, Maria Luisa,Stella, Lorenzo American Chemical Society 2014 ACS CHEMICAL BIOLOGY Vol.9 No.9
<P>Antimicrobial peptides (AMPs) kill bacteria mainly through the perturbation of their membranes and are promising compounds to fight drug resistance. Models of the mechanism of AMPs-induced membrane perturbation were developed based on experiments in liposomes, but their relevance for bacterial killing is debated. We determined the association of an analogue of the AMP PMAP-23 to <I>Escherichia coli</I> cells, under the same experimental conditions used to measure bactericidal activity. Killing took place only when bound peptides completely saturated bacterial membranes (10<SUP>6</SUP>–10<SUP>7</SUP> bound peptides per cell), indicating that the “carpet” model for the perturbation of artificial bilayers is representative of what happens in real bacteria. This finding supports the view that, at least for this peptide, a microbicidal mechanism is possible <I>in vivo</I> only at micromolar total peptide concentrations. We also showed that, notwithstanding their simplicity, liposomes represent a reliable model to characterize AMPs partition in bacterial membranes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/acbcct/2014/acbcct.2014.9.issue-9/cb500426r/production/images/medium/cb-2014-00426r_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cb500426r'>ACS Electronic Supporting Info</A></P>
Bobone, Sara,Roversi, Daniela,Giordano, Lorenzo,De Zotti, Marta,Formaggio, Fernando,Toniolo, Claudio,Park, Yoonkyung,Stella, Lorenzo American Chemical Society 2012 Biochemistry Vol.51 No.51
<P>Antimicrobial peptides usually kill bacteria by making their membranes permeable. Two main models (barrel-stave and Shai–Matsuzaki–Huang) have been proposed to describe the peptide-induced pores. Although several experimental tests can be exploited to discriminate between these two models, the dependence of peptide activity on lipid properties (intrinsic curvature and membrane thickness) is routinely used for this purpose. Here, we show that, contrary to what is currently accepted, this criterion is unreliable.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bichaw/2012/bichaw.2012.51.issue-51/bi3015086/production/images/medium/bi-2012-015086_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bi3015086'>ACS Electronic Supporting Info</A></P>