Hemoglobin Bougardirey-Mali beta 119 (GH2) Gly replaced by Val. An electrophoretically silent variant migrating in isoelectrofocusing as Hb F.
Hemoglobin Bougardirey-Mali was detected by isoelectrofocusing during a screening in a 32 years old African, a native of Mali. This abnormal Hb, representing 35% of the total, exhibited the same pI as that of Hb F. In contrast, it was indistinguishable from Hb A in all the electrophoretic systems tested, and equally by its resistance to alkaline denaturation. Structural studies have shown that the abnormality was localized on the beta chain. A fingerprint of the tryptic digest of the aminoethylated beta chain indicated the absence of the beta T12 b. The presence of an abnormal beta T12 b was suspected in the T14-15 spot, as indicated by the intensity of staining and its amino acid composition. beta T12 b was isolated by chromatography on PA 35. Its sequential analysis by manual Edman-dansyl degradation showed that glycine 119 was replaced by a valine residue. This mutation is localized in a alpha 1 beta 1 contact, which makes the molecules slightly unstable. The clinical consequences of this mutation seem to be minor; similar observations have been reported for the other Hb mutated at the same locus, i.e. Hb Fannin-Lubbock beta 119 Gly leads to Asp.