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Dynamic Turn Conformation of a Short Tryptophan-Rich Cationic Antimicrobial Peptide and its Interaction with Phospholipid Membranes
Matthew Nichols , Miljan Kuljanin , Mostafa Nategholeslam , Tuan Hoang , Shaghayegh Vafaei , Bruno Tomberli , Chris G Gray , Lillian DeBruin , and Masoud Jelokhani-Niaraki, J. Phys. Chem. B, 2013, 117, 14697-14708.
DOI: 10.1021/jp4096985
Publication Date (Web): November 6, 2013
Copyright © 2013 American Chemical Society

Cationic antimicrobial peptides are promising sources for novel therapeutic agents against multidrug-resistant bacteria. HHC-36 (KRWWKWWRR) is a simple but effective antimicrobial peptide with similar or superior activity compared to several conventional antibiotics. In this biophysical study, unique conformational properties of this peptide and some of its analogs as well as its interaction with lipid membranes are investigated in detail. Circular dichroism (CD) and molecular dynamics modelling studies of HHC-36 in different environments reveal a dynamic amphipathic structure composed of competing turn conformations with free energies lower than that of the unfolded state, implying a strong influence of tryptophan interactions in formation of the turns. CD spectra and gel electrophoresis also show strong evidence for self-association of this peptide in aqueous milieu and interaction with both neutrally- and negatively-charged lipid membrane systems. Isothermal titration calorimetry and acrylamide fluorescence quenching experiments emphasize the preference of HHC-36 for negatively-charged vesicles. In addition, dye leakage experiments suggest that this peptide functions through a surface-associated mechanism with weak lytic activity against bacterial model membranes.