Membrane thickness and the mechanism of action of the short peptaibol trichogin GA IV

• Published in: Biochimica et biophysica acta Vol. 1828; no. 3; pp. 1013 - 1024
• Main Authors: Bobone, S., Gerelli, Y., De Zotti, M., Bocchinfuso, G., Farrotti, A., Orioni, B., Sebastiani, F., Latter, E., Penfold, J., Senesi, R., Formaggio, F., Palleschi, A., Toniolo, C., Fragneto, G., Stella, L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2013
• Subjects: Amino Acids - chemistry; Biophysics - methods; Cell Membrane - chemistry; Cell Membrane - metabolism; Computer Simulation; Dose-Response Relationship, Drug; Hydrophobic and Hydrophilic Interactions; Lipid Bilayers - chemistry; Lipopeptides - chemistry; Membrane Lipids - chemistry; Membrane thickness; Molecular Conformation; Molecular Dynamics Simulation; Molecular dynamics simulations; Nanoparticles; Neutron reflectivity; Neutrons; Peptaibiotics; Peptide embedding in a bilayer; Peptides - chemistry; Protein Structure, Tertiary; Transmembrane peptides; DIEA; nOct; Alm; CF; HFIP; AMP; Transmembrane peptides; EDC; Peptaibiotics; Peptide embedding in a bilayer; GAIV; Lol; SLD; Molecular dynamics simulations; SMH; Neutron reflectivity; MD; POPC; Fmoc; Aib; HATU; HOAt; DMF; Membrane thickness
• ISSN: 0005-2736; 0006-3002; 1879-2642; 1878-2434
• DOI: 10.1016/j.bbamem.2012.11.033

Trichogin GA IV (GAIV) is an antimicrobial peptide of the peptaibol family, like the extensively studied alamethicin (Alm). GAIV acts by perturbing membrane permeability. Previous data have shown that pore formation is related to GAIV aggregation and insertion in the hydrophobic core of the membrane. This behavior is similar to that of Alm and in agreement with a barrel-stave mechanism, in which transmembrane oriented peptides aggregate to form a channel. However, while the 19-amino acid long Alm has a length comparable to the membrane thickness, GAIV comprises only 10 amino acids, and its helix is about half the normal bilayer thickness. Here, we report the results of neutron reflectivity measurements, showing that GAIV inserts in the hydrophobic region of the membrane, causing a significant thinning of the bilayer. Molecular dynamics simulations of GAIV/membrane systems were also performed. For these studies we developed a novel approach for constructing the initial configuration, by embedding the short peptide in the hydrophobic core of the bilayer. These calculations indicated that in the transmembrane orientation GAIV interacts strongly with the polar phospholipid headgroups, drawing them towards its N- and C-termini, inducing membrane thinning and becoming able to span the bilayer. Finally, vesicle leakage experiments demonstrated that GAIV activity is significantly higher with thinner membranes, becoming similar to that of Alm when the bilayer thickness is comparable to its size. Overall, these data indicate that a barrel-stave mechanism of pore formation might be possible for GAIV and for similarly short peptaibols despite their relatively small size. [Display omitted] ► The short peptaibol trichogin GAIV inserts in the core of the membrane. ► Once inserted, it causes a significant thinning of the bilayer. ► According to simulations, this is due to its interaction with lipid headgroups. ► Its activity increases dramatically in thinner membranes. ► It might form barrel-stave channels, like the longer peptaibol alamethicin.