Deduced amino acid sequence (top) and topologic model for RhD^VI type I protein (bottom). The CE portion of D^VI type I protein encoded by exons 4 and 5 is underlined and its specific amino acid changes from positions 169-267 are marked by asterisks. (B) Hypothetical organization of D^VI type I protein in the erythrocyte plasma membrane. Of the 12 potential membrane-spanning segments, the CE portion would form three passes (C6-C8) and the D portion would contribute to the remaining. The fourth extracellular loop is solely derived from the CE portion and its E allelic specificity is indicated by a 226Pro residue. N and C denote the amino and carboxyl terminal ends.