Protein stability and conformational rearrangements in lipid bilayers: linear gramicidin, a model system.

AUTOR(ES)

Cotten, M

RESUMO

The replacement of four tryptophans in gramicidin A by four phenylalanines (gramicidin M) causes no change in the molecular fold of this dimeric peptide in a low dielectric isotropic organic solvent, but the molecular folds are dramatically different in a lipid bilayer environment. The indoles of gramicidin A interact with the anisotropic bilayer environment to induce a change in the molecular fold. The double-helical fold of gramicidin M, as opposed to the single-stranded structure of gramicidin A, is not compatible with ion conductance. Gramicidin A/gramicidin M hybrid structures have also been prepared, and like gramicidin M homodimers, these dimeric hybrids appear to have a double-helical fold, suggesting that a couple of indoles are being buried in the bilayer interstices. To achieve this equilibrium structure (i.e., minimum energy conformation), incubation at 68 degrees C for 2 days is required. Kinetically trapped metastable structures may be more common in lipid bilayers than in an aqueous isotropic environment. Structural characterizations in the bilayers were achieved with solid-state NMR-derived orientational constraints from uniformly aligned lipid bilayer samples, and characterizations in organic solvents were accomplished by solution NMR.

Documentos Relacionados

• Mean-field calculations of chain packing and conformational statistics in lipid bilayers: comparison with experiments and molecular dynamics studies.
• Phase topology and percolation in two-component lipid bilayers: a monte Carlo approach.
• Internal electrostatic potentials in bilayers: measuring and controlling dipole potentials in lipid vesicles.
• Gramicidin, Valinomycin, and Cation Permeability of Streptococcus faecalis
• Proton conduction in gramicidin A and in its dioxolane-linked dimer in different lipid bilayers.