Simulation of voltage-dependent interactions of alpha-helical peptides with lipid bilayers.
Pore formation in lipid bilayers by channel-forming peptides and toxins is thought to follow voltage-dependent insertion of amphipathic alpha-helices into lipid bilayers. We have developed an approximate potential for use within the CHARMm molecular mechanics program which enables one to simulate voltage-dependent interaction of such helices with a lipid bilayer. Two classes of helical peptides which interact with lipid bilayers have been studied: (a) delta-toxin, a 26 residue channel-forming peptide from Staphylococcus aureus; and (b) synthetic peptides corresponding to the alpha 5 and alpha 7 helices of the pore-forming domain of Bacillus thuringiensis CryIIIA delta-endotoxin. Analysis of delta-toxin molecular dynamics (MD) simulations suggested that the presence of a transbilayer voltage stabilized the inserted location of delta-toxin helices, but did not cause insertion per se. A series of simulations for the alpha 5 and alpha 7 peptides revealed dynamic switching of the alpha 5 helix between a membrane-associated and a membrane-inserted state in response to a transbilayer voltage. In contrast the alpha 7 helix did not exhibit such switching but instead retained a membrane associated state. These results are in agreement with recent experimental studies of the interactions of synthetic alpha 5 and alpha 7 peptides with lipid bilayers.
Biggin
P C
PC
Laboratory of Molecular Biophysics, University of Oxford, UK.
Sansom
M S
MS
D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000737:chemistry*; D004563:Electrochemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D013816:Thermodynamics
D001427:Bacterial Toxins; D008051:Lipid Bilayers; C025971:staphylococcal delta toxin