Analogous oligo‐acyl‐lysines with distinct antibacterial mechanisms

Abstract

Bactericidal properties were recently shown to emerge from hydrophobicity and charge buildup in oligo-acyl-lysine (OAK) peptide mimetics. Toward understanding the attributes that govern the activity of this novel antimicrobial system, we compared the functional and mechanistic properties of a known octamer and a newly generated hexamer analog. The data provide strong evidence for multiple similarities that included high tissue stability, low hemolysis, large-spectrum antibacterial activity in vitro, and the ability to prevent Escherichia coli-induced mortality in vivo. Despite these similarities, however, the octamer mode of action involved membrane disruption, unlike the hexamer, which acted predominantly through inhibition of DNA functions with characteristically slower bactericidal kinetics. Collectively, the data support the view that the analogous OAKs induced bacterial death by distinct mechanisms and further suggest that relatively minor differences in the sequence of host defense peptides are responsible for selecting one mechanism over another, possibly in conjunction with differential binding affinities to the external and/or cytoplasmic membrane.

Amphibian antimicrobial peptide fallaxin analogue FL9 affects virulence gene expression and DNA replication in Staphylococcus aureus

“…Some AMPs that inhibit DNA synthesis bind nonspecifically to DNA. For example, the amphibian AMP, the a-helical AMP buforin II, can penetrate the cell membrane without causing its disruption, and inhibits cellular functions by binding to nucleic acids (Park et al, 1998;Kobayashi et al, 2000;Rotem et al, 2008;Sarig et al, 2011;Gottschalk et al, 2013). Therefore, to investigate whether the inhibition of DNA synthesis could be due to the binding of FL9 to bacterial DNA, a gel retardation assay was performed.…”

“…In addition to membrane disruption, several studies have shown that some AMPs also have the ability to traverse the cytoplasmic membrane and target intracellular molecules such as DNA and RNA (Brogden, 2005;Jenssen et al, 2006;Peschel & Sahl, 2006;Makobongo et al, 2012 interaction of AMPs with DNA may damage DNA and induce the SOS response (Gunderson & Segall, 2006;Rotem et al, 2008;Sarig et al, 2011). The SOS regulon comprises genes essential for DNA repair and restart of stalled or collapsed replication forks.…”

Antibacterial Properties and Mode of Action of a Short Acyl-Lysyl Oligomer

“…The bacteria were cultured in suitable broth medium (brain heart infusion or LB). The MIC was determined using a slightly modified NCLSI microdilution assay (44) to enable comparison with previously characterized OAKs (42)(43)(44)(45)(46). For pH and salt variations, the culture medium was brought to the desired pH by adding NaOH or HCl (1 N) or to the desired saline concentration by adding NaCl to the culture medium.…”

“…The DNA binding assay was performed using pUC19 plasmids that were extracted from E. coli K-12, as previously described (46). Briefly, the plasmids were preincubated with the OAKs at the specified concentrations (1 h; 37°C), followed by washes and incubation with the DNase BamHI (1 h; 37°C).…”

“…Two types of OAKs have been presented so far, each composed of acyl-lysyl (␣ n ) or lysyl-acyl-lysyl (␤ n ) subunits, where n defines the acyl length (43). In previous studies, the ␣-OAKs C 12 K-7␣ 8 (44) and C 12 K-5␣ 8 (46) showed potent antibacterial activity against most gram-negative strains tested, both in vitro and in vivo. Furthermore, the OAKs were shown to induce bacterial death by damaging the cytoplasmic membrane or by inhibiting DNA expression, respectively.…”