Molecular Biology of the Anion Exchanger Gene Family

This chapter reviews data on the structure and function of the anion exchanger (AE) gene family with a focus on the structure and organization of the anion exchanger genes and the conservation of function among the polypeptides they encode. It describes the expression of the band 3 gene in erythroid cells and some of the biochemical, pharmacological, and immunological evidence for expression of the anion exchanger gene family in nonerythroid tissues. The gene family of AE consists of at least four or five members, of which three are characterized at the cDNA level. AE1–3 encode polypeptides that share significant homology with the erythrocyte anion exchanger, band 3 (AE1). The expression of cDNAs encoding these genes in heterologous systems confirms that this sequence similarity is reflected in the capacity to mediate reversible Cl/HCO 3 exchange. The NH 2 -terminal domain of band 3 interacts with several cytoplasmic proteins in erythrocytes. AE2 is expressed in a number of epithelial and nonepithelial cells. AE3 is expressed in excitable tissues, including neurons and muscle. These proteins play a role in the regulation of intracellular pH and chloride in their respective tissue.