Journal
BIOPHYSICAL JOURNAL
Volume 99, Issue 8, Pages 2507-2515Publisher
CELL PRESS
DOI: 10.1016/j.bpj.2010.05.038
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Funding
- Deutsche Forschungsgemeinschaft [SFB266]
- Max Planck Society
- Agence National de la Recherche (TRANSPEP)
- Vaincre la Mucoviscidose
- Louis Pasteur University (University of Strasbourg)
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Brazil
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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 His(10)-Ala(13). 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 alpha-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.
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