Hemoglobin Dallas (alpha 97(G4)Asn-->Lys): functional characterization of a high oxygen affinity natural mutant. |
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| Authors: | E Lendaro R Ippoliti A Brancaccio A Bellelli B Vallone G Ivaldi G V Sciarratta C Castello S Tomova M Brunori |
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| Institution: | CNR, Center of Molecular Biology, University La Sapienza, Rome, Italy. |
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| Abstract: | Hemoglobin Dallas, an alpha-chain variant with a substitution of lysine for asparagine at position 97(G4), was found to have increased oxygen affinity (p1/2 = 1 mmHg at pH 7.3 and 20 degrees C), diminished cooperativity (n, the Hill coefficient = 1.7) and reduced Bohr effect (about 50%). Addition of allosteric effectors (such as 2,3-diphosphoglycerate, inositol hexakisphosphate and bezafibrate) led to a decrease in oxygen affinity and increase in cooperative energy. Kinetic studies at pH 7.0 and 20 degrees C revealed that (i), the overall rate of oxygen dissociation is 1.4-fold slower than that for HbA and (ii), the carbon monoxide dissociation rate is unaffected. The abnormal properties of this hemoglobin variant can be attributed to a more 'relaxed' T-state. |
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