A STRUCTURAL STUDY OF LOW-DENSITY LIPOPROTEIN-GANGLIOSIDE COMPLEXES USING THE INDUCTIVE RESONANCE ENERGY-TRANSFER FROM TRYPTOPHAN RESIDUES TO PYRENE

The interaction of low density lipoproteins (LDL) with ganglioside GM(3) immobilized on plastic was shown to result in the formation of LDL-GM(3) complexes. It has been shown that pyrene incorporates into these complexes in the same way as in native lipoproteins. Using the phenomenon of inductive resonance energy transfer from excited tryptophan residues to pyrene, it has been established that tryptophan residues of the apo-B molecule in the LDL-GM(3) complex are more deeply immersed in the lipid phase than those of LDL. The degree of immersion was proportional to the ganglioside content of the complex. Estimation of the degree of accessibility of tryptophyls to pyrene (fluorescence quenching) has shown that, when LDL interact with GM(3), a structural reconstruction of the protein occurs with the formation of domains more than 37 Angstrom in size (1.2 Forster's radios).