Melittin-GM1 interaction: A model for a side-by-side complex

We report here the interaction of melittin with ganglioside GM1 by steady-state fluorescence, one-dimensional H-1 NMR spectroscopy and molecular modeling. In the presence of GM1 the emission maximum of melittin is blue shifted and fluorescence quenching efficiencies of iodide and acrylamide are substantially reduced, indicating a shielding of tryptophan of melittin from aqueous environment. Significant line broadening of NMR resonances of melittin, suggestive of motional restriction, is observed. Molecular modeling indicates a melittin-GM1 complex with N-terminal hydrophobic stretch of melittin associating with the ceramide tail and C-terminal hydrophilic end of melittin having favorable electrostatic interaction with the carbohydrate head group of GM1. (C) 2002 Elsevier Science (USA).