title: Hydroxy-tryptophan containing derivatives of tritrpticin: modification of antimicrobial activity and membrane interactions.
abstract: Tritrpticin is an antimicrobial peptide with a strong microbicidal activity against Gram-positive and Gram-negative bacteria as well as fungi. The 13-residue peptide is essentially symmetrical and possesses a unique cluster of three Trp residues near the center of its amino acid sequence. The mechanism of action of tritrpticin is believed to involve permeabilization of the cytoplasmic membrane of susceptible bacteria. However it has been suggested that intracellular targets may also play a role in its antimicrobial activity. In this work the mechanism of action of several tritrpticin derivatives was studied through substitution of the three Trp residues with 5-hydroxy-tryptophan (5OHW), a naturally occurring non-ribosomal amino acid. Although it is more polar, 5OHW preserves many of the biophysical and biochemical properties of Trp, allowing the use of fluorescence spectroscopy and NMR techniques to study the interaction of the modified peptides with membrane mimetics. Single or triple 5OHW substitution did not have a large effect on the MIC of the parent peptide against Escherichia coli and Bacillus subtilis. However, the mechanism of action was altered by simultaneously replacing all three Trp with 5OHW. Our results suggest that the inner membrane of Gram-negative bacteria did not constitute the main target of this particular tritrpticin derivative. Since the addition of a hydroxyl group to the indole motif of the Trp residue was able to modify the mechanism of action of the peptides, our data confirm the importance of the Trp cluster in tritrpticin. This work also shows that 5OHW constitutes a new probe to modulate the antimicrobial activity and mechanism of action of other Trp-rich antimicrobial peptides.
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Arias
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Katharine V
authors.initials: KV
authors.lastname: Jensen
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Leonard T
authors.initials: LT
authors.lastname: Nguyen
authors.affiliation: Microbiology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Storey
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada. Electronic address: vogel@ucalgary.ca.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D006916:5-Hydroxytryptophan; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000187:drug effects*; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000494:pharmacology*; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
chemical_list: D000890:Anti-Infective Agents; D009842:Oligopeptides; D010455:Peptides; C402895:tritrpticin; D004247:DNA; D006916:5-Hydroxytryptophan
keywords: 5-Hydroxy-tryptophan; Antimicrobial peptide; Membrane interaction; Membrane permeabilization; Tritrpticin