BAND-3 MEMPHIS VARIANT-II - ALTERED STILBENE DISULFONATE BINDING AND THE DIEGO (DI(A)) BLOOD-GROUP ANTIGEN ARE ASSOCIATED WITH THE HUMAN ERYTHROCYTE-BAND 3 MUTATION PRO(854)-]LEU

Band 3 Memphis is a commonly occurring polymorphic form of the human r ed cell anion transporter (band 3, AE1). Band 3 Memphis migrates more slowly on an SDS-polyacrylamide gel than normal band 3 and results fro m a point mutation Lys(56) --> Glu. TWO types of band 3 Memphis, varia nts I and II, can be distinguished by their susceptibility to covalent labeling with H2DIDS (4,4'-diisothiocyanato-2,2'-dihydrostilbene disu lfonate). Memphis variant II is more readily labeled than Memphis vari ant I or normal band 3. The Memphis variant II is also associated with the presence of the Diego (Di(a)) blood group antigen on the red cell s. We have shown that Memphis variant II carries the polymorphism Pro( 854) --> Leu as well as Lys(56) --> Glu. The blood group antigen (Di(a )) present at the surface of Memphis variant II type red cells suggest s the mutation Pro(854) --> 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 Pro(854) --> Leu affects the reactivity of Lys(539) to covalent reaction with H2DIDS.