Erythroid band 3 variants and disease.

This review describes some of the naturally occurring band 3 (AEI) variants and their association with disease. Southeast Asian Ovalocytic (SAO) band 3, an inactive and misfolded protein, is probably only maintained in certain populations because it provides protection against the cerebral form of malaria. Many mutations that cause instability of band 3, either at the mRNA or protein level, result in hereditary spherocytosis (HS). Some polymorphisms alter amino acid residues in the extracellular loops of band 3 and are associated with blood group antigens. A truncated form of AEI is expressed in kidney cells and certain AEI mutations are associated with distal renal tubular acidosis (dRTA). The molecular basis of these variants and their effect on the structure and function of band 3 are discussed. The association between band 3 and glycophorin A (GPA) and the structure/function changes of band 3 in the absence of GPA are also described.