NMR structures of the histidine-rich peptide LAH4 in micellar environments: membrane insertion, pH-dependent mode of antimicrobial action, and DNA transfection

Biophys J. 2010 Oct 20;99(8):2507-15. doi: 10.1016/j.bpj.2010.05.038.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antimicrobial Cationic Peptides / chemistry*
  • Antimicrobial Cationic Peptides / metabolism*
  • Antimicrobial Cationic Peptides / pharmacology
  • Cell Membrane / metabolism*
  • DNA / genetics
  • DNA / metabolism*
  • Histidine*
  • Hydrogen-Ion Concentration
  • Magnetic Resonance Spectroscopy
  • Micelles*
  • Models, Molecular
  • Molecular Sequence Data
  • Phosphates / chemistry
  • Phosphorylcholine / analogs & derivatives
  • Phosphorylcholine / chemistry
  • Protein Structure, Secondary
  • Temperature
  • Transfection*
  • Trifluoroethanol / chemistry


  • Antimicrobial Cationic Peptides
  • Micelles
  • Phosphates
  • Phosphorylcholine
  • Histidine
  • dodecylphosphocholine
  • Trifluoroethanol
  • DNA