Hb Barika [alpha42(C7)Tyr-->His (alpha2)] leads to an alpha+ -Thalassemia-like syndrome

In human deoxyhemoglobin (deoxyHb), the hydrogen bond between Aspbeta99(G1) and Tyralpha42(C7), located in the alpha1beta2 interface, is crucial for the stability of the T structure. All the variants that could arise from a single point mutation affecting codon beta99 have already been observed, leading always to erythrocytosis. Conversely, up to now, Hb Barika is the only example found in a patient in whom the alpha42 is mutated. From a biochemical point of view, for theoretical reasons, this substitution has already been extensively studied on recombinant hemoglobin (rHb). In the patient, Hb Barika is expressed at a level lower than expected for an alpha2 gene variant and leads to an alpha+-thalassemic-like syndrome.