A NEW FAST-MOVING VARIANT CAUSING ERYTHROCYTOSIS AND MILD HEMOLYSIS -HB-GAMBARA[BETA-82(EF6)LYS-]GLU]

Hb Gambara is a new hemoglobin variant with abnormal beta chains that has been found in three out of four members of a family of Lombardy or igin (Gambara, Brescia, Northern Italy). The affected subjects led a n ormal life, but they had modest erythrocytosis and mild (compensated) hemolysis with slight splenomegaly. Their abnormal hemoglobin was abou t 52% of the total hemoglobin, and was shown to be stable by the isopr opanol test. Whole blood P-50 of the proband was 19.3 Torr, Bohr effec t was decreased (-0.25), as well as the molar ratio between the 2,3-di phosphoglycerate level and total hemoglobin of erythrocytes (0.68). Th e purified abnormal hemoglobin was characterized by an altered oxygen affinity, low n-factor, chloride, and 2,3-diphosphoglycerate effects. The Bohr effect was about 40% of the normal control. The abnormal hemo globin moved faster than Hb A at alkaline electrophoresis, and split i nto two fractions, probably due to the formation of hybrid tetramers ( alpha(2) beta(A) beta(X)). Th, reversed phase high performance liquid chromatogram from the tryptic digest of the aminoethylated abnormal be ta chain subunits indicated the presence of an extra peptide, beta T-9 ,10, replacing the individual peptides beta T-9 and beta T-10. Finally , the proband's DNA, drawn from a suitable segment of the beta structu ral gene (exon 2), revealed a nucleotide sequence carrying the heteroz ygous mutation (A) under bar AG-->(G) under bar AG at codon 82. This l ed to a Lys-->Glu substitution at position 82(EF6) of the beta chain.