The structure of α-haemoglobin in complex with a haemoglobin-binding domain from Staphylococcus aureus reveals the elusive α-haemoglobin dimerization interface

Publication Type:
Journal Article
Acta Crystallographica Section F:Structural Biology Communications, 2014, 70 (8), pp. 1032 - 1037
Issue Date:
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Adult haemoglobin (Hb) is made up of two α and two β subunits. Mutations that reduce expression of the α- or β-globin genes lead to the conditions α- or β-thalassaemia, respectively. Whilst both conditions are characterized by anaemia of variable severity, other details of their pathophysiology are different, in part owing to the greater stability of the β chains that is conferred through β self-association. In contrast, α subunits interact weakly, and in the absence of stabilizing quaternary interactions the α chain (α) is prone to haem loss and denaturation. The molecular contacts that confer weak self-association of α have not been determined previously. Here, the first structure of an α 2 homodimer is reported in complex with one domain of the Hb receptor from Staphylococcus aureus. The α 2 dimer interface has a highly unusual, approximately linear, arrangement of four His side chains within hydrogen-bonding distance of each other. Some interactions present in the α1β1 dimer interface of native Hb are preserved in the α 2 dimer. However, a marked asymmetry is observed in the α 2 interface, suggesting that steric factors limit the number of stabilizing interactions that can form simultaneously across the interface. © 2014 CrossMark.
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