Enhanced Membrane Disruption and Antibiotic Action against Pathogenic Bacteria by Designed Histidine-Rich Peptides at Acidic pH

Abstract

The histidine-rich amphipathic cationic peptide LAH4 has antibiotic and DNA delivery capabilities. Here, we explore the interaction of peptides from this family with model membranes as monitored by solid-state 2 H nuclear magnetic resonance and their antibiotic activities against a range of bacteria. At neutral pH, the membrane disruption is weak, but at acidic pH, the peptides strongly disturb the anionic lipid component of bacterial membranes and cause bacterial lysis. The peptides are effective antibiotics at both pH 7.2 and pH 5.5, although the antibacterial activity is strongly affected by the change in pH. At neutral pH, the LAH peptides were active against both methicillin-resistant and -sensitive Staphylococcus aureus strains but ineffective against Pseudomonas aeruginosa. In contrast, the LAH peptides were highly active against P. aeruginosa in an acidic environment, as is found in the epithelial-lining fluid of cystic fibrosis patients. Our results show that modest antibiotic activity of histidine-rich peptides can be dramatically enhanced by inducing membrane disruption, in this case by lowering the pH, and that histidine-rich peptides have potential as future antibiotic agents.With the dramatic rise of antibiotic resistance in pathogenic bacteria, there is no doubt that there is an urgent requirement for the development of novel antibiotics. The lungs of cystic fibrosis patients are chronically infected by lineages of Pseudomonas aeruginosa with high mutation rates that can readily become resistant to current antibiotics (20,25), while the impact of methicillin-resistant Staphylococcus aureus (MRSA) has been well documented (2). These bacteria, therefore, represent significant targets for new classes of antibiotics.Cationic antimicrobial peptides play a central role in preventing the onset of infection in many organisms, and following the introduction of a number of such peptides in clinical trials (16), it seems likely that development of these peptides will provide the basis for a new class of antibiotics. LAH4, a histidine-rich amphipathic ␣-helical peptide (4), has been shown to possess both antibiotic (34) and DNA delivery (17, 18) capabilities. This dual functionality could be exploited in therapeutic strategies for a number of diseases, a notable example being cystic fibrosis, where LAH4 or a derivative thereof could form part of a gene delivery vehicle while concomitantly fighting microbial infections that result from the underlying condition. Therefore, a fundamental understanding of the antibiotic strategies employed by cationic antimicrobial peptides such as LAH4 will aid the design of more powerful antibiotics that may eventually become frontline treatments for a variety of infectious diseases.To understand in greater detail how histidine-rich peptides operate against their microbial targets, we synthesized a series of derivatives of LAH4 and combined biophysical studies of their interactions using model membranes from solid-state nuclear magnetic resonance (NMR) of chain-deuterated lipid...

Low pH Enhances the Action of Maximin H5 against Staphylococcus aureus and Helps Mediate Lysylated Phosphatidylglycerol-Induced Resistance

“…On the other hand, PMF dependent efflux pumps also appear able to import porcine, bovine and other AMPs, thereby promoting their activity [112][113][114] . The promotion of antimicrobial action by low pH has been reported for a number of AMPs, including human hepcidins 115 , gads 116 clavanins and styelins 117 from marine organisms, and a range of synthetic peptides [118][119][120][121] , along with the anticancer activity of a variety of AMPs 16 . For the most, part, these studies have focussed on cationic AMPs and there has been less research into the effects of pH on anionic AMPs 94,95 .…”

Anthrax toxin-induced rupture of artificial lipid bilayer membranes

“…Interestingly, the addition of a His6-tag increases the binding strength of LF N by approximately threefold at pH c|t 5.5|5.5 75 and restores the binding activity to neutral and negatively charged mutants of LF N 27. 125 His residues are also responsible for pH-dependent rearrangement of proteins, such as the pHdependent coil-helix transition of glycinamide ribonucleotide transformylase, 126 acidic activation of His-rich synthetic peptides aimed at disrupting microbial membranes, 127 and enhancing gene transfer though membrane permeabilization of human tumor cells. There are several potential interactions that may contribute to the destabilization of the membrane spanning region of the PA 63 pore and the membrane.…”

Concerted Protonation of Key Histidines Triggers Membrane Interaction of the Diphtheria Toxin T Domain

“…The pH ranges at which these transitions occur suggest that the protonation of His side chains may be involved. Indeed, it has been shown that His residues may function as pH sensors for many molecular mechanisms involving protein-membrane interaction (11,12) and/or MG formation (13,14).…”