Band 3 Memphis variant II. Altered stilbene disulfonate binding and the Diego (Dia) blood group antigen are associated with the human erythrocyte band 3 mutation Pro854-->Leu.

Band 3 Memphis is a commonly occurring polymorphic form of the human red cell anion transporter (band 3, AE1). Band 3 Memphis migrates more slowly on an SDS-polyacrylamide gel than normal band 3 and results from a point mutation Lys56-->Glu. Two types of band 3 Memphis, variants I and II, can be distinguished by their susceptibility to covalent labeling with H2DIDS (4,4'-diisothiocyanato-2,2'-dihydrostilbene disulfonate). Memphis variant II is more readily labeled than Memphis variant I or normal band 3. The Memphis variant II is also associated with the presence of the Diego (Dia) blood group antigen on the red cells. We have shown that Memphis variant II carries the polymorphism Pro854-->Leu, as well as Lys56-->Glu. The blood group antigen (Dia) present at the surface of Memphis variant II type red cells suggests the mutation Pro854-->Leu causes a change in the structure of an extracellular loop of Memphis variant II band 3. We discuss possible ways in which the mutation Pro854-->Leu affects the reactivity of Lys539 to covalent reaction with H2DIDS.