Solution structure of a designed amphipathic antimicrobial synthetic peptide, PGAa

A designed peptide, PGAa showed an excellent anti-fungal activity as well as an efficient bactericidal activity toward gram-positive, especially in the pathogenic yeast Candida albicans 28838. The solution structures of PGAa have been determined both in 40% TFE/water solution and DPC micelle by CD and NMR spectroscopy. Based on NOEs, vicinal coupling constants, backbone amide exchange rates, and chemical shift indices, PGAa formed a long amphipathic α-helical conformation in both TFE and DPC micelle environments, spanning the residues Ile²-Ala¹⁹ in TFE and Lys⁵-Ala¹⁹ in DPC micelle, respectively. Solution structures suggested that the hydrophobic residues would interact with the fatty acyl chains of the lipid bilayer, while the positively charged side-chains exposed to aqueous environments. Therefore, we conclude that the ≃-helical structure as well as the highly amphiphatic nature of PGAa peptide may play a critical role in its antimicrobial activity as well as selectivities in different species. (C) 2000 Academic Press.