NMR structures of the histidine-rich peptide LAH4 in micellar environments: membrane insertion, pH-dependent mode of antimicrobial action, and DNA transfection.
The LAH4 family of histidine-rich peptides exhibits potent antimicrobial and DNA transfection activities, both of which require interactions with cellular membranes. The bilayer association of the peptides has been shown to be strongly pH-dependent, with in-planar alignments under acidic conditions and transmembrane orientations when the histidines are discharged. Therefore, we investigated the pH- and temperature-dependent conformations of LAH4 in DPC micellar solutions and in a TFE/PBS solvent mixture. In the presence of detergent and at pH 4.1, LAH4 adopts helical conformations between residues 9 and 24 concomitantly with a high hydrophobic moment. At pH 6.1, a helix-loop-helix structure forms with a hinge encompassing residues His¹⁰-Ala¹³. The data suggest that the high density of histidine residues and the resulting electrostatic repulsion lead to both a decrease in the pK values of the histidines and a less stable α-helical conformation of this region. The hinged structure at pH 6.1 facilitates membrane anchoring and insertion. At pH 7.8, the histidines are uncharged and an extended helical conformation including residues 4-21 is again obtained. LAH4 thus exhibits a high degree of conformational plasticity. The structures provide a stroboscopic view of the conformational changes that occur during membrane insertion, and are discussed in the context of antimicrobial activity and DNA transfection.
Institut de Chimie, Université de Strasbourg/Centre National de Recherche Scientifique, France.
Julia
J
Georgescu
Victor H O
VH
Munhoz
Burkhard
B
Bechinger
D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010710:Phosphates / Q000737:chemistry; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000737:chemistry; D017433:Protein Structure, Secondary; D013696:Temperature; D014162:Transfection; D014270:Trifluoroethanol / Q000737:chemistry
D023181:Antimicrobial Cationic Peptides; D008823:Micelles; D010710:Phosphates; D010767:Phosphorylcholine; D006639:Histidine; C028810:dodecylphosphocholine; D014270:Trifluoroethanol; D004247:DNA