Quantitative and functional analysis of the C-terminal 4.1R variants.

Red cell membrane proteins were fractionated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), stained with Coomassie blue, and analyzed densitometrically. (A) Total protein 4.1R expression was measured as the ratio of protein 4.1R to protein 4.2. (B) The 2 truncated protein 4.1R variants (4.1R Coimbra and 4.1R Presles) and the normal 4.1R produced in trans in the heterozygous patients were estimated separately. WT and Mut indicate wild-type and mutated protein 4.1R, respectively. Note that the expression levels of both normal 4.1R are very similar (WT 4.1/4.2 bars), whereas 4.1R Coimbra is produced in a significantly lower amount than 4.1R Presles (Mut 4.1 bars). (C) Osmotic gradient ektacytometric curves. DI indicates deformability index; A, control; B, 4.1R Coimbra heterozygote (family member B2); C, 4.1R Algiers heterozygote 21; D, 4.1R Coimbra homozygote (patient B1); and E, 4.1R Algiers homozygote.21 Each 4.1R Coimbra allele yields a partial deficiency of 4.1R. Each 4.1R Algiers allele yields a complete deficiency of 4.1R.