Role of Aromatic Amino Acids in Lipopolysaccharide and Membrane Interactions of Antimicrobial Peptides for Use in Plant Disease Control

Abstract

KYE28 (KYEITTIHNLFRKLTHRLFRRNFGYT-LR), the representative sequence of helix D of heparin co-factor II, was demonstrated to be potent against agronomically important Gram-negative plant pathogens Xanthomonas vesicatoria and Xanthomonas oryzae, capable of inhibiting disease symptoms in detached tomato leaves. NMR studies in the presence of lipopolysaccharide provided structural insights into the mechanisms underlying this, notably in relationship to outer membrane permeabilization. The three-dimensional solution structure of KYE28 in LPS is characterized by an N-terminal helical segment, an intermediate loop followed by another short helical stretch, and an extended C terminus. The two termini are in close proximity to each other via aromatic packing interactions, whereas the positively charged residues form an exterior polar shell. To further demonstrate the importance of the aromatic residues for this, a mutant peptide KYE28A, with Ala substitutions at Phe 11 , Phe 19 , Phe 23 , and Tyr 25 was designed, which showed attenuated antimicrobial activity at high salt concentrations, as well as lower membrane disruption and LPS binding abilities compared with KYE28. In contrast to KYE28, KYE28A adopted an extended helical structure in LPS with extended N and C termini. Aromatic packing interactions were completely lost, although hydrophobic interaction between the side chains of hydrophobic residues were still partly retained, imparting an amphipathic character and explaining its residual antimicrobial activity and LPS binding as observed from ellipsometry and isothermal titration calorimetry. We thus present key structural aspects of KYE28, constituting an aromatic zipper, of potential importance for the development of novel plant protection agents and therapeutic agents.

Antibacterial mechanisms of GN‐2 derived peptides and peptoids against Escherichia coli

“…Therefore, the pi‐stacking interactions promoted by aromatic residues are not necessary for LPS binding suggesting that only hydrophobicity (and charge) is relevant for this interaction. This is in contrast to the reported relevance of aromatic residues in AMP and LPS binding …”

Modification Targeting the “Rana Box” Motif of a Novel Nigrocin Peptide From Hylarana latouchii Enhances and Broadens Its Potency Against Multiple Bacteria

“…Taken these into consideration, C-terminal amidation of the modified peptide may also facilitate to its antimicrobial activity by stabilizing membrane interactive peptide structure and improving the partial charge of the modified analog. Last but not least, a phenylalanine residue might also provide extra membrane- binding driving force for nigrocin-HLM since it contains an aromatic ring (Lee et al, 2013; Datta et al, 2016). …”

Short Antimicrobial Peptides Exhibiting Antibacterial and Anti‐Inflammatory Activities Derived from the N‐Terminal Helix of Papiliocin

“…Similarly, cupiennins mutated with an alanine or lysine in place of phenylalanine residues in their N‐terminal region exhibited decreased lipid‐bilayer interaction . Additionally, Datta et al showed that disruption of aromatic packing in the KYE28 peptide attenuated its antibacterial activity …”