title: Mechanism of action of puroindoline derived tryptophan-rich antimicrobial peptides.
abstract: A tryptophan (Trp)-rich region in the wheat endosperm protein, puroindoline A, was previously shown to possess potent antimicrobial activity against Gram-positive and Gram-negative bacteria and this was attributed to the peptide inducing membrane instability. In the present work, the antimicrobial activity of the corresponding Trp-rich region in the puroindoline B isoform was examined and its antimicrobial activity was characterized. Unexpectedly, the puroindoline B Trp-rich peptide (PuroB) was relatively inactive compared to the related puroindoline A peptide (PuroA), despite strong sequence similarity. Using the sequence of PuroA as a template, a series of PuroB variants were synthesized and the antimicrobial activity was restored. Interestingly, all of these PuroB peptides preferentially interacted with negatively charged phospholipids, but unlike PuroA, they did not disrupt the integrity of lipid bilayers. This suggests that the primary mode of action of the PuroB peptides involves an antimicrobial target other than the bacterial membrane. Further tests revealed that all of the puroindoline derived peptides bind deoxyribonucleic acid (DNA) and block macromolecular synthesis in vivo. Based on these results, it appears that the interaction between puroindoline derived peptides and membranes is only an initial step in the mode of action and that binding to intracellular targets, such as DNA and ribonucleic acid (RNA), contributes significantly to their antimicrobial mode of action.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada. evan@hancocklab.com
authors.forename: Evan F
authors.initials: EF
authors.lastname: Haney
authors.forename: Alexandra P
authors.initials: AP
authors.lastname: Petersen
authors.forename: Cheryl K
authors.initials: CK
authors.lastname: Lau
authors.forename: Weiguo
authors.initials: W
authors.lastname: Jing
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Storey
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects*; D008051:Lipid Bilayers / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D010743:Phospholipids / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry*; D012313:RNA / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013211:Staphylococcus aureus / Q000187:drug effects*; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D010743:Phospholipids; D010940:Plant Proteins; C082942:puroindoline protein, Triticum aestivum; D012313:RNA; D014364:Tryptophan; D004247:DNA