Haemoglobin (Hb) J-Sardegna [α50(CE8)His → Asp] is a haemoglobin variant characteristic of subjects from the island of Sardinia. Here we report a study of the functional properties of both fetal and adult Hb J-Sardegna. The results indicate that adult Hb J-Sardegna displays an oxygen affinity that is higher than that of adult Hb only in the presence of 2,3-diphosphoglycerate (2,3-DPG). On the contrary, at 20 °C, the oxygen affinity of fetal Hb J-Sardegna is identical to that of normal fetal haemoglobin, both in the presence and in the absence of 2,3-DPG. A significant difference between these two systems (i.e. a higher oxygen affinity of fetal Hb J-Sardegna) shows up very clearly only when temperature is increased to 37 °C. Hence in fetal Hb, the main effect of the amino acid substitution is a decrease in the overall enthalpy change of oxygenation. The results outline the role of the α1-β1 interface in assessing the thermodynamics of oxygen binding. The functional properties of both adult and fetal Hb J-Sardegna have been interpreted at the structural level in light of the results obtained by a computational modelling approach performed in comparison with HbA and Hb Aichi, a variant characterized by a different mutation [α50(CE8)His → Arg] at the same position.
Adult and fetal haemoglobin J-Sardegna [α50(CE8)His→Asp]: functional and molecular modelling studies
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Marcella CORDA, Maria C. DE ROSA, Maria G. PELLEGRINI, Maria T. SANNA, Alessandra OLIANAS, Antonella FAIS, Laura MANCA, Bruno MASALA, Bruno ZAPPACOSTA, Silvana FICARRA, Massimo CASTAGNOLA, Bruno GIARDINA; Adult and fetal haemoglobin J-Sardegna [α50(CE8)His→Asp]: functional and molecular modelling studies. Biochem J 15 February 2000; 346 (1): 193–199. doi: https://doi.org/10.1042/bj3460193
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