Antimicrobial activity of a porphyrin binding peptide

Abstract

Amphiphilic alpha-helices are common motifs used in numerous biological systems including membrane channels/pores and antimicrobial peptides (AMPs), and binding proteins, and a variety of synthetic biomaterials. Previously, an amphiphilic peptide with lysine-containing motifs was shown to reversibly bind the anionic porphyrin meso-Tetra(4-sulfonatophenyl)porphyrin (TPPS42−) and promote the formation of excitonically coupled conductive J-aggregates. The work presented here focuses on the use of this amphiphilic peptide and derivatives as a potential antimicrobial agent. AMPs are naturally occurring components of the innate immune system, which selectively target and kill bacteria. Sequence derivatives were synthesized in which the position of the Trp, used as a fluorescence reporter, was changed. Additional variants were synthesized where the hydrophobic amino acids were replaced with Ala to reduce net hydrophobicity or where the cationic Lys residues were replaced with diaminopropionic acid (Dap). All peptide sequences retained the ability to bind TPPS42− and promote the formation of J-aggregates. The peptides all exhibited a preference for binding anionic lipid vesicles compared to zwitterionic bilayers. The Trp position did not impact antimicrobial activity, but the substituted peptides exhibited markedly lower efficacy. The Dap-containing peptide was only active against E. coli and P. aeruginosa, while the Ala-substituted peptide was inactive at the concentrations tested. This trend was also evident in bacterial membrane permeabilization. The results indicate that the amphiphilic porphyrin binding peptides can also be used as antimicrobial peptides. The cationic nature is a driver in binding to lipid bilayers, but the overall hydrophobicity is important for antimicrobial activity and membrane disruption.

Investigation of the structure‐activity relationship in ponericin L1 from Neoponera goeldii

“…Lipid binding assays were carried out as performed previously. [ 44 ] Briefly, the samples contained 2 μM peptide in PBS buffer (150 mM NaCl, 50 mM Na 2 HPO 4 ; pH 7.0) and were titrated with a lipid vesicle stock (0.5 or 1.0 mM concentration). All binding assays used excitation at 280 nm and an emission range of 300 to 400 nm.…”

“…Using a series of well‐characterized biophysical/spectroscopic measurements as well as microbiological and cellular assays, the activity of these L1 sequences was investigated. [ 14,17,38‐44 ] Due to the inherent environmental sensitivity of Trp fluorescence emission, the native Trp in the L1 sequence (W6) was exploited as a spectroscopic probe for the oligomerization in solution, bilayer binding, and bilayer orientation of peptides. Antibacterial, bacterial membrane permeabilization, and hemolysis assays were also conducted to evaluate the activity of these sequences against natural biological membranes.…”

Correlating Lipid Membrane Permeabilities of Imidazolium Ionic Liquids with Their Cytotoxicities on Yeast, Bacterial, and Mammalian Cells

“…Growth inhibition of E. coli and S. aureus was investigated using the standard minimal inhibitory concentration (MIC) assay [44,45]. For P. aeruginosa we used cell line ATCC10145 and followed a literature procedure for growth [46]. Cultures of bacteria were grown by inoculating 3 mL of LB broth with a single colony from the streaked plates and allowing the culture to grow overnight at 37 °C with shaking.…”

Characterization and Antimicrobial Activity of Amphiphilic Peptide AP3 and Derivative Sequences

“…Tryptophan fluorescence quenching was performed using the collisional quencher acrylamide, which can strongly quench tryptophan exposed to the aqueous environments. However, previous results show acrylamide causes very minimal quenching of tryptophan residues buried in the nonpolar core of the bilayer [31,37,38]. Quenching of the peptides was compared in the presence and absence of lipid vesicles.…”