We have previously described the antibacterial capacity of protegrin-1 (PG-1), a cysteine-rich, cationic peptide from porcine leukocytes, against Neisseria gonorrhoeae. We now report genetic and biochemical evidence that gonococcal susceptibility to the lethal action of PG-1 and other structurally unrelated antibacterial peptides, including a peptide (LL-37) that is expressed constitutively by human granulocytes and testis and inducibly by keratinocytes, is modulated by an energy-dependent eff lux system termed mtr. These results indicate that such eff lux systems may enable mucosal pathogens like gonococci to resist endogenous antimicrobial peptides that are thought to act during infection.

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Graphical Abstract Highlights d CRISPR screening identified FcRn as an essential and universal EV-B receptor d FcRn facilitates EV-B uncoating and CD55 for attachment d High-resolution Cryo-EM structures described the mechanism of virus entry d The molecular mechanism of dual (attachment versus uncoating) receptor-usage was illustrated SUMMARY a structural basis for understanding the mechanisms of enterovirus entry.

We purified a molecule from the murine small intestine that killed both Escherichia coli and Listeria monocytogenes, and identified it as intestinal phospholipase A2 (iPLA2) by NH2-terminal sequencing and enzymatic measurements. The ability of iPLA2 to kill. L monocytogenes was greatly enhanced by 5 mM calcium, inhibited by EGTA and abolished after reduction and alkylation, suggesting that enzymatic activity was required for iPLA2-mediated bactericidal activity. A mouse-avirulent phoP mutant, S. typhimunium 7953S, was 3.5-fold more susceptible to iPLA2 than its isogenic virulent parent, S. typhimurium 14028S (estimated minimal bactericidal concentrations 12.7±0.5 jig/ml vs. 43.9±4.5 jig/ml,