Interaction between glycophorin and a spin-labeled cholesterol analogue in reconstituted dimyristoylphosphatidylcholine bilayer vesicles.

The interaction between glycophorin and a spin-labeled cholesterol analogue has been investigated by EPR spectroscopy. In vesicles which were reconstituted by the freeze and thaw technique, direct evidence was obtained for a reorganisation of the membrane at low protein content (protein/lipid ratio less than 1:300). From the spin exchange interaction we were able to show a protein-induced clustering of the steroid in fluid and in gel state membranes. Tryptic cleavage of the complete N-terminus of glycophorin vanishes the effect. Whereas the removal of the sialic acid residues by neuraminidase digest had no influence on the EPR spectra. The interaction seems to be cholestane spin label specific since it was not observed with an androstane spin-label.