Rotational diffusion of band 3 in membranes from ovalocytic and malaria-infected erythrocytes as studied by time-resolved phosphorescence anisotropy

摘要

Time-resolved phosphorescence anisotropy has been used to follow the rotational diffusion of band 3, the major integral membrane protein of erythrocytes. The rate of rotational diffusion is exquisitely sensitive to protein-protein interactions which increase the size of the rotating species. In membranes prepared from normal human erythrocytes, band 3 appears to exist as a heterogeneous population of aggregates with different mobilities. Restriction of band 3 motion is probably due, at least in part, to interactions with the peripheral membrane protein, ankyrin. Surprisingly, the further linkage of ankyrin to spectrin in the underlying cytoskeleton does not appear to influence band 3 mobility. We have found that band 3 has a highly restricted mobility in membranes prepared from malaria-infected erythrocytes. This decreased rotational freedom of band 3 correlates with a decrease in deformability and an altered morphology. Band 3 mobility was also assessed in the membranes of Melanesian ovalocytes. These malaria-resistant erythrocytes from donors in Papua New Guinea show a three-fold decrease in deformability. The decreased deformability and ovalocytic shape of these erythrocytes was found to be associated with a dramatic decrease in band 3 mobility.