Association of hemoglobin chains with the cell membrane as a cause of red cell distortion in thalassemia

Hemoglobin chains were separated and their interaction with membrane ghosts was studied using their ability to quench the fluorescence intensity of a membrane embedded probe. It was observed that α chains bind faster and with higher affinity to the membrane sites than do β chains. The fast reversible interaction of both chains with the membrane was followed by a time-dependent partial loss of reversibility. Band 3 cytoplasmic fragments (B3F) were isolated and their reaction with separated Hb chains was studied using fluorescence quenching techniques as well. The data demonstrate that the relative affinity of the chains for B3F and loss of reversibility of the reaction followed patterns similar to the corresponding interaction of the chains with whole membranes. Band 3 cytoplasmic poles are therefore suggested as the high-affinity sites on the membrane for hemoglobin chains. When globin was reacted with B3F, it was observed that this protein binds strongly to the same membrane sites, but practically irreversibly. Exchange of the HbA content of normal cells by separated α or β chains resulted in membrane distortions in both cases, but α chains caused greater morphological changes than did β chains. The results of this study may provide one explanation for the differences in the thalassemia syndromes when excess of either α or β chains is involved.