A new hemoglobin variant altering the α1β2 contact: Hb Chemilly α2β2 99(G1)Asp→Val

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Abstract
Hemoglobin Chemilly (α2β2 99(G1)Asp→Val), a high oxygen affinity variant, was uncovered in the red blood cells of a polycythemic patient who reported to the hospital concerning periodic headaches. We describe the molecular abnormality and functional studies of this new abnormal Hb. β 99(G1)Asp, an invariant residue of hemoglobin, is considered a key amino acid for conformational changes between the R⇆T quaternary structures responsible for the allosteric behavior of hemoglobin. Hb Chemilly exhibits a high 02 affinity, very low cooperativity and reduced Bohr effect. Its functional abnormalities are compared to the 5 other Hb variants at site β 99(G1) described up to now of the 7 single base substitutions predictable from the genetic code.