Effects of diethyl ether on membrane lipid ordering and on rotational dynamics of the anion exchange protein in intact human erythrocytes: correlations with anion exchange function.

The roles of lipid ordering and protein dynamics on the function of the anion exchange protein (band 3) in intact human erythrocytes have been investigated. The effects of diethyl ether on the ordering of membrane lipids and on the rotational dynamics of band 3 were measured by EPR and saturation-transfer EPR spectroscopies, respectively, and correlated with the anion exchange function of band 3. With increasing concentration, diethyl ether monotonically decreased the ordering of membrane lipids near the polar head-group region, as reported by the lipid-soluble spin probe 5-doxylstearic acid, but produced comparatively little change in the ordering of lipids in the hydrophobic midzone, as reported by 16-doxylstearic acid. The rotational mobility of band 3, as reported by the affinity spin-label bis(sulfo-N-succinimidyl) doxyl-2-spiro-5'-azelate [Anjaneyulu et al. (1989) Biochemistry 28, 6583-6590], also increased monotonically with increasing ether concentration. This increase in rotational mobility was not due to a demonstrable change in its state of oligomerization, since band 3 was readily cross-linked by bis(sulfo-N-succinimidyl) suberate to covalent dimers in the presence or absence of ether. At concentrations up to 2 vol % ether, hemolysis of erythrocytes was negligible, and the spectroscopic changes observed were completely reversed following its removal. Km, Vmax, and Eact. for sulfate uptake into chloride-loaded erythrocytes were not significantly affected by addition of ether.(ABSTRACT TRUNCATED AT 250 WORDS)