The antimicrobial peptide GL13K encompasses 13 amino acid residues and has been designed and optimized from the salivary protein BPIFA2 to exhibit potent bacteriocidal and anti-biofilm activity against Gram-negative and Gram-positive bacteria as well as anti-lipopolysaccharide activity in vitro and in vivo. Here, the peptide was analyzed in a variety of membrane environments by circular dichroism spectroscopy and by high-resolution multidimensional solution nuclear magnetic resonance (NMR) spectroscopy. Whereas in the absence of membranes a random coil conformation predominates, the peptide adopts a helical structure from residue 5 to 11 in the presence of dodecylphosphocholine micelles. In contrast, a predominantly β-sheet structure was observed in the presence of lipid bilayers carrying negatively charged phospholipids. Whereas 15N solid-state NMR spectra are indicative of a partial alignment of the peptide 15N-1H vector along the membrane surface, 2H and 31P solid-state NMR spectra indicate that in this configuration the peptide exhibits pronounced disordering activities on the phospholipid membrane, which is possibly related to antimicrobial action. GL13K, thus, undergoes a number of conformational transitions, including a random coil state in solution, a helical structure upon dilution at the surface of zwitterionic membranes, and β-sheet conformations at high peptide:lipid ratios.
Bibliographical noteFunding Information:
This research was supported by Grant 1R01DE017989 from the National Institute for Dental and Craniofacial Research (S.-U.G.), Grant GM 64742 from the National Institute for General Medical Sciences (G.V.), and a fellowship supported by Grant R90DE023058 from the National Institute of Dental and Craniofacial Research (X.C.). Research funds were provided by the University of Minnesota School of Dentistry (S.-U.G.) and The Office of the Vice-president for Research at the University of Minnesota Project 55466 of the Grant-in-Aid of Research, Artistry and Scholarship Program (C. Aparicio). B.B. was supported by a sabbatical stay at the University of Minnesota School of Dentistry that was generously supported by the Schools Lasby Visiting Professor Fellowship and the University of Strasbourg. B.B. received additional support from the Agence Nationale de la Recherche (Projects TRANSPEP 07-PCV-0018 membraneDNP 12-BSV5-0012, and MemPepSyn 14-CE34-0001-01 and the LabEx Chemistry of Complex Systems 10-LABX-0026-CSC), the RTRA International Center of Frontier Research in Chemistry, the French Foundation for Medical Research (FRM), the University of Strasbourg, the CNRS, and the Region Alsace.
© 2017 American Chemical Society.