The self-association of melittin and its binding to lipids: An intrinsic fluorescence polarization study

Abstract

Intrinsic fluorescence has proved to be very useful for studying protein-protein or lipid-protein interactions [l--8 J. Although these studies are mostly restricted to the analysis of intensity or wavelength changes in the emission spectra, polarization measurements can afford valuable information, as shown in the self-association of apo-lipoproteins [7,8] and the interaction of glucagon with lipids [5,6]. Here, intrinsic fluorescence polarization is applied to the study of the self-association of mellitin, and of its binding to lipids. Melittin is a small amphipathic peptide of 26 residues, extracted from bee venom, which is known to have a direct lytic activity on living cells [9-l 1 J. It contains only one fluorescent residue, Trp,,, and its emission spectrum is very sensitive to interactions with lipids [I ,3].