Resonance energy transfer study of hemoglobin and cytochrome c complexes with lipids

AbstractThe complexes of hemoglobin and cytochrome c with liposomes composed of phosphatidylcholine and its mixtures with cardiolipin and cholesterol have been studied by monitoring resonance energy transfer between fluorescent probe 3-methoxybenzanthrone as donor and heme groups of the proteins as acceptors. By analyzing experimental data within the framework of the model of energy transfer in two-dimensional systems, the limits of the range of possible heme positions with respect to lipid bilayer have been assessed. The distance of heme group of hemoglobin from the membrane center was found to increase in the presence of cardiolipin or cholesterol. The results obtained for cytochrome c complexes with cardiolipin-containing model membranes suggest the existence of preferential protein orientation relative to the lipid bilayer, and provide evidence for the protein penetration in the membrane interior