Highly purified CD71 protein was isolated from human placental trophoblasts and Molt-4 cells with affinity chromatography and was shown with SDS-PAGE as an obvious protein band of 90 ×103u under reducing condition and about 180 × 103u under non-reducing condition. The protein molecules were reconstituted into artificial membranes composed of different ratios of phospholipids (PL)/cholesterol (Ch). Circular dichroism analysis demonstrated that there was a decrease of the beta-laminar structure and an increase of alpha-helica and random coils when the Ch content of the artificial membranes DMPC/Ch or DOPC/Ch was increased. Tryptophan fluorescence spectrum also demonstrated that along with the changes of the lipid constituents of the artificial membrane,the spatial conformation of CD71 protein underwent corresponding changes.
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