Using Fluorous Amino Acids To Probe the Effects of Changing Hydrophobicity on the Physical and Biological Properties of the β-Hairpin Antimicrobial Peptide Protegrin-1

Abstract

Protegrins are potent members of the beta-hairpin-forming class of antimicrobial peptides. Key to their antimicrobial activity is their assembly into oligomeric structures upon binding to the bacterial membrane. To examine the relationship between the physicochemical properties of the peptide and its biological activity, we have synthesized variants of protegrin-1 in which key residues in the hydrophobic core, valine-14 and -16, are changed to leucine and to the extensively fluorinated analogue hexafluoroleucine. These substitutions have the effect of making the peptide progressively more hydrophobic while minimally perturbing the secondary structure. The leucine-containing peptide was significantly more active than wild-type protegrin against several common pathogenic bacterial strains, whereas the hexafluoroleucine-substituted peptide, in contrast, showed significantly diminished activity against several bacterial strains. Isothermal titration calorimetry measurements revealed significant changes in the interaction of the peptides binding to small unilamelar vesicles that mimic the lipid composition of the bacterial membrane. The binding isotherms for wild-type and leucine-substituted protegrins indicate that electrostatic interactions dominate the membrane-peptide interaction, whereas the isotherm for the hexafluoroleucine-substituted protegrin suggests a diminished electrostatic component to binding. Notably both of these substitutions appear to alter the stoichiometry of the lipid-peptide interaction, suggesting that these substitutions may stabilize oligomerized forms of protegrin that are postulated to be intermediates in the assembly of the beta-barrel membrane pore structure.

Strand Length-Dependent Antimicrobial Activity and Membrane-Active Mechanism of Arginine- and Valine-Rich β-Hairpin-Like Antimicrobial Peptides

“…7). The VR1 spectra demonstrated significantly more ␤-turns in 30 mM SDS micelles, with minima between 200 and 205 nm and maxima between 225 and 230 nm (11). In TFE, VR1 and VR2 exhibited a population having a ␤-hairpin conformation characterized by a negative ellipticity near 205 nm and a crossover at 200 nm (44).…”

Cysteine deleted protegrin-1 (CDP-1): Anti-bacterial activity, outer-membrane disruption and selectivity

“…In particular, a large difference in MIC values for Gram-negative bacteria between RR11 and LR10 peptides indicates critical role of residue R4 in bacterial selectivity. It may be noted that an N-terminal deletion analog, of the RGGR sequence motif, of PG-1 has also exhibited a significant loss of bactericidal activity [37].…”

“…Among five members, protegrin-1 (PG-1) has drawn considerable attention for antimicrobial drug development [32][33][34][35][36][37]. Iseganan or IB367 an analog of PG-1 has been evaluated in a phase three clinical trial for oral mucositis [34].…”

Cuantificación de la efectividad de la indolicidina y protegrina-4 por medio de análisis de parámetros cinéticos

“…De las cinco protegrinas conocidas, la protegrina-1 (PG-1) ha atraído considerablemente la atención para el diseño de nuevos péptidos antimicrobianos (Kokryakov et al, 1993;Gottler et al, 2008). Por ejemplo, el análogo de la PG-1 conocida cómo Iseganan o IB367 se ha evaluado en ensayos clínicos contra la mucosis oral (Tamamura et al, 1995).…”