Alamethicin Aggregation in Lipid Membranes

作者：Pan Jianjun; Tristram Nagle Stephanie; Nagle John F^*

来源：Journal of Membrane Biology, 2009, 231(1): 11-27.

DOI：10.1007/s00232-009-9199-8

• Alamethicin
• Aggregation
• Hydrophobic mismatch
• Water pore
• Helix bundle
• Ion channel

X-ray scattering features induced by aggregates of alamethicin (Alm) were obtained in oriented stacks of model membranes of DOPC(diC18:1PC) and diC22:1PC. The first feature obtained near full hydration was Bragg rod in-plane scattering near 0.11 angstrom(-1) in DOPC and near 0.08 angstrom(-1) in diC22: 1PC at a 1: 10 Alm: lipid ratio. This feature is interpreted as bundles consisting of n Alm monomers in a barrel-stave configuration surrounding a water pore. Fitting the scattering data to previously published molecular dynamics simulations indicates that the number of peptides per bundle is n = 6 in DOPC and n C 9 in diC22:1PC. The larger bundle size in diC22:1PC is explained by hydrophobic mismatch of Alm with the thicker bilayer. A second diffuse scattering peak located at q(r) approximate to 0.7 angstrom(-1) is obtained for both DOPC and diC22:1PC at several peptide concentrations. Theoretical calculations indicate that this peak cannot be caused by the Alm bundle structure. Instead, we interpret it as being due to two-dimensional hexagonally packed clusters in equilibrium with Alm bundles. As the relative humidity was reduced, interactions between Alm in neighboring bilayers produced more peaks with three-dimensional crystallographic character that do not index with the conventional hexagonal space groups.

• 出版日期2009-9