Novel studies on a "silent" high affinity mutant hemoglobin (San Diego, beta 109 Val replaced by Met)

A patient with a "silent" mutant hemoglobin characterized by high oxygen affinity and erythrocytosis is described. A novel approach was used to identify the mutant chain. Functionally active alpha and beta chains were prepared from hemolysates of the patient and a normal control. Hybrid tetramers of patient's beta chain were prepared. Functional studies revealed that the patient's beta chains had a higher oxygen affinity (P50, 1.1 torr) than normal beta chains (P50, 1.7 torr) and the hybrid containing the patient's beta chains had a P50 similar to the patient's "stripped" hemolysate. It was assumed therefore that the mutation was in the beta chain; structural studies using cyanogen bromide cleavage revealed that the patient had Hb San Diego, beta 109 Val replaced by Met, and that the patient's cells contained approximately 50 percent mutant hemoglobin.