Peptidomimetic Antibiotics Target Outer-Membrane Biogenesis in Pseudomonas aeruginosa

Abstract

Antibiotics with new mechanisms of action are urgently required to combat the growing health threat posed by resistant pathogenic microorganisms. We synthesized a family of peptidomimetic antibiotics, based on the antimicrobial peptide protegrin I. Several rounds of optimization gave a lead compound that was active in the nanomolar range against gram-negative Pseudomonas sp., but was largely inactive against other Gram-negative and Gram-positive bacteria. Biochemical and genetic studies showed the peptidomimetics had a non-membrane-lytic mechanism of action and identified a homologue of the ß-barrel protein LptD (Imp/OstA), which functions in outer membrane biogenesis, as a cellular target. The peptidomimetic showed potent antimicrobial activity in a mouse septicemia infection model. Drug-resistant strains of Pseudomonas are a serious health problem, so this family of antibiotics may have important therapeutic applications. A synthesized antibiotic targets a protein involved in outer membrane biogenesis to selectively kill Pseudomonas pathogens. 1 Peptidomimetic Antibiotics Target Outer Membrane Biogenesis in Pseudomonas aeruginosa AbstractAntibiotics with new mechanisms of action are urgently required to combat the growing health

Structural studies of β-hairpin peptidomimetic antibiotics that target LptD in Pseudomonas sp.

“…[1] A ß-hairpin-shaped peptide might be especially well suited to bind to proteins rich in ß-structure, such as LptD. For example, the ß-strands in each ligand might interact with exposed edges of antiparallel ß-sheets in the ß-barrel target protein.…”

“…[1] Similar accumulations of membrane-like material are seen in E. coli and P. aeruginosa when lptD, or other essential genes in the Lpt pathway, are downregulated, most likely due to the accumulation of LPS molecules in the IM. [5e, 10] To aid understanding of how the peptidomimetic antibiotics interact with LptD, we report here NMR studies of the solution structure of the cyclic peptide L27-11 ( Figure 1A).…”

“…[1] The amino acid sequence of L27-11 is unrelated to that of any known naturally occurring host-defense cationic antimicrobial peptide (CAP), although like many CAPs it does contain a mix of hydrophobic (aromatic) and cationic residues. [2] The peptidomimetics do not cause lysis of bacterial cell membranes, and only the enantiomer shown has antimicrobial activity in the nanomolar range against Pseudomonas sp.…”

“…Related molecules with optimized drug-like properties include POL7001, which has a much-improved stability towards proteolysis in human plasma due to the replacement of multiple Lys/Arg residues by diaminobutyric acid (Dab). [1] These substitutions do not have a large effect on antimicrobial activity, but remove cleavage sites for trypsin-like proteases. A related peptide called POL7080 is now in clinical development, and has recently completed successfully a human phase I clinical trial.…”

“…[4] These peptidomimetic antibiotics have a novel mechanism of action, involving an interaction with the outer membrane (OM) protein LptD. [1] The function of LptD in Gram-negative bacteria has been studied most thoroughly in Escherichia coli, where it plays an essential role in lipopolysaccharide (LPS) transport to the cell surface. [5] Seven essential Lpt (lipopolysaccharide transport) proteins are known to mediate LPS transport from the inner membrane (IM), where the final steps of LPS assembly occur, to the outer leaflet of the asymmetric OM.…”