Agglutination of human erythrocytes by the interaction of Zn2+ion with histidine-651 on the extracellular domain of band 3

Abstract

Clustering of band 3, chloride/bicarbonate exchanger, has been reported in Zn2+-treated human erythrocytes. However, the agglutination of human erythrocytes is also induced by the interaction of Zn2+ion with histidine on band 3. Identification of histidine that interacts with Zn2+ion remains to be determined. The Zn2+-induced agglutination of human erythrocytes was unaffected by chymotrypsin cleavage of the small loop region containing His-547 in the extracellular domain of band 3. On the other hand, papain digestion of the large loop region containing His-651 in band 3 inhibited such Zn2+-induced agglutination. Moreover, Zn2+-induced erythrocyte agglutination was inhibited by the peptide (ARGWVIHPLG) containing His-651, but not by the peptide such as ARGWVIRPLG, which His-651 was substituted by arginine. Among 10 kinds of animal erythrocytes tested, interestingly, no agglutination by Zn2+ions was observed in cow cells only that the forth amino acid in the upstream from His-669 on the large loop of cow band 3 is aspartate (Asp-665) instead of glycine. As expected, the agglutination of human erythrocytes by Zn2+ ions was inhibited in the presence of aspartate. These data indicate that the interaction of Zn2+ ion with His-651 residue of band 3 plays an important role in the Zn2+-induced agglutination of human erythrocytes.