MUTATIONS OF CONSERVED ARGININES IN THE MEMBRANE DOMAIN OF ERYTHROID BAND-3 LEAD TO A DECREASE IN MEMBRANE-ASSOCIATED BAND-3 AND TO THE PHENOTYPE OF HEREDITARY SPHEROCYTOSIS

To elucidate the molecular basis of band 3 deficiency in a recently de fined subset of patients with autosomal dominant hereditary spherocyto sis (HS), we screened band 3 cDNA for single-strand conformation polym orphism (SSCP). In 5 of 17 (29%) unrelated HS subjects with band 3 def iciency, we detected substitutions R760W, R760O, R808C, and R870W that were all coinherited with the HS phenotype. The involved arginines ar e highly conserved throughout evolution. To examine whether or not the product of the mutant allele is inserted into the membrane, we studie d one HS subject who was doubly heterozygous for the R760Q mutation an d the K56E (band 3(MEMPHIS)) polymorphism that results in altered elec trophoretic mobility of the band 3 Memphis proteolytic fragments. We d etected only the band 3(MEMPHIS) in the erythrocyte membrane indicatin g that the protein product of the mutant, R760Q, band 3 allele is abse nt from the red blood cell membrane. These findings suggest that the R 760Q substitution, and probably the other arginine substitutions, prod uce band 3 deficiency either by precluding incorporation of the mutant protein into the red blood cell membrane or by leading to loss of mut ant protein from differentiating erythroid precursors. (C) 1995 by The American Society of Hematology.