Membrane potential enhances the entry of a short AMP into bacterial cells and lipid vesicles

What is it about?

It is considered that a short antimicrobial peptide (AMP) (RRWQWR), derived from lactoferricin B (LfcinB), [LfcinB(4-9)], is a cell-penetrating peptide (CPP)-type AMP (Biochemistry, 56, 4419, 2017). In this paper, we investigated the effect of membrane potential on the entry of this peptide into the bacterial cytoplasm, the spheroplasts, and the lumen of giant unilamellar vesicles (GUVs) comprising the E. coli polar lipid extract without damaging their membranes.

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Why is it important?

In this paper, we found that at low peptide concentrations, a fluorescent probe-labeled LfcinB(4-9) [i.e., Rh-LfcinB(4-9)] entered the cytoplasm of E. coli cells and their spheroplasts without pore formation in their cell membranes, but a H+ ionophore suppressed this entry. We also observed that Rh-LfcinB(4-9) entered the lumen of GUVs comprising E. coli polar lipid extract (i.e., E. coli lipid-GUVs) without pore formation and the rate of its entry increased with an increase in negative membrane potential of the GUV membrane.  These data directly indicate that negative membrane potential enhances the entry of this peptide into E. coli cells, their spheroplasts, E. coli lipid-GUVs, and thus, its bactericidal activity.