Cecelia A. Reynolds

Hemoglobin Louisville (β42 (CD1) Phe→Leu): an unstable variant causing mild hemolytic anemia

An unstable hemoglobin variant termed Hb Louisville, was found in four members of a Caucasian family, who were suffering from a mild hemolytic anemia. The variant showed a decreased stability upon warming at 65 degrees C and an increased tendency to dissociate in the presence of sulfhydryl group-blocking agents. The structural abnormality was identified as a replacement of phenylalanyl residue in position 42 (CD1) by a leucyl residue. Substitution of this phenylalanyl residue, which participates in the contact with heme, by a nonpolar leucyl residue has apparently less severe consequences than a replacement of the same residue by a polar seryl residue as in Hb Hammersmith. Oxygen equilibrium studies of total hemolysate from one Hb Louisville heterozygote indicated a decreased oxygen affinity, a marked decrease in heme-heme interaction, and a normal Bohr effect. Studies with isolated Hb Louisville were not made because it was not possible to separate the variant from normal Hb A.

Hemoglobin Savannah (B6(24) β-glycine→valine): an unstable variant causing anemia with inclusion bodies

An abnormal hemoglobin, termed Hb Savannah, was found in red cell hemolysate of a young Caucasian girl with severe hemolytic anemia. The presence of this unstable variant became evident when inclusion bodies appeared rapidly upon exposure of red cells to redox dyes and a large percentage of hemoglobin in hemolysate precipitated on warming to 65°C. Treatment of the hemoglobin with p-hydroxymercuribenzoate (PMB) caused a rapid dissociation into monomers; starch-gel electrophoresis of PMB-treated hemoglobin showed the presence of abnormal β-chains. Data from structural studies of isolated β-chains indicated substitution of a valyl residue for the normally occurring glycyl residue at position 24, which corresponds to helical residue B6. A similar substitution but with an arginine replacing the glycyl residue has been observed in Hb Riverdale-Bronx. The glycine to valine substitution will change the relationship of the B and the E helices which results in extensive conformational changes in the β-chain. This change presumably causes an increased dissociation of the hemoglobin molecule into dimers and probably monomers, and a decreased stability of the αβ-dimers. The hemoglobin abnormality may be the result of a fresh mutation because the abnormality is not present in the parents nor in any of the seven siblings.

Hemoglobin A2-indonesia or α2δ269(E13)Gly→Arg

Abstract Structural studies of an abnormal minor hemoglobin, termed Hb-A 2 -Indonesia, have shown that in this δ chain variant the glycine residue in position 69 (position 13 of the Helix E) is replaced by an arginine residue. Hb-A 2 -Indonesia differs from Hb-A 2 ′ or α 2 δ 2 16 Gly → Arg in antigenic properties because a specific anti-Hb-A 2 ′ antibody did not react with Hb-A 2 -Indonesia.

Hb-Genova (α2β228(bio)leu→pro); methods for detection and analysis of unstable hemoglobins

Abstract The third occurrence of the unstable β chain variant Hb-Genova is described. The variant is characterized by replacement of a leucyl residue in position 28(B 10) by a prolyl residue. The abnormality was discovered in a Canadian woman of Ukrainian ancestry, who had a persistent anemia with Heinz bodies prevalent since early childhood. The techniques used in the detection of unstable hemoglobins are reviewed.