Characterization of weak alleles at the DIA1 locus (Mustapha 1, Mustapha 2, and Mustapha 3) in the Algerian population

One percent of the Algerian population carries a weak allele at the DIA₁ locus, responsible for a 50% decrease of red cell soluble cytochrome b₅ reductase activity. Quantitative abnormalities of the soluble and the membrane-bound enzyme have been investigated in the red cells and in the leukocytes of seven subjects considered to be heterozygous at the DIA₁ locus. Conventional electrophoretic or isoelectrophoretic studies did not show any qualitative abnormality. However, continuous titration obtained by combined IEF-electrophoresis displayed in five out of seven subjects a discrete abnormal line on the titration curve compatible with an Arg?His substitution. In fact, at least three types of weak alleles could be defined by combining the qualitative and quantitative results obtained with the erythrocyte (soluble and membrane-bound) and leukocyte enzyme. We call these subgroups DIA Mustapha₁, DIA Mustapha₂, and DIA Mustapha₃.