BAND-3 MOBILITY IN CAMELID ELLIPTOCYTES - IMPLICATIONS FOR ERYTHROCYTE SHAPE

Measurements of time-resolved phosphorescence anisotropy were used to monitor the rotational diffusion of eosin-labeled band 3 in membranes of the elliptocytic erythrocytes of alpacas and camels. The rotational freedom of camelid band 3 was more restricted than for human band 3. Removal of the peripheral membrane proteins from human erythrocyte mem branes, by high-pH treatment, increased the band 3 rotational freedom. The same high-pH treatment of alpaca and camel erythrocyte membranes failed to alter the rotational freedom of band 3 in these species and also failed to remove ankyrin. Treatment of human and alpaca erythrocy te membranes with trypsin, which removed the cytoplasmic domain of ban d 3, caused a marked increase in band 3 rotational freedom in both spe cies. We suggest that ankyrin may modulate the rotational freedom of b and 3 in camelid erythrocytes, thereby influences the erythrocyte shap e and deformability. The rotational freedom of band 3 in sheep, pig, a nd rat erythrocyte membranes was also examined and found to be slightl y greater than for human band 3. This is consistent with the inability of glyceraldehyde-3-phosphate dehydrogenase to bind to band 3 in the erythrocyte membranes of these species.