Fluoride and azide binding to ferric human hemoglobin:haptoglobin complexes highlights the ligand-dependent inequivalence of the α and ß hemoglobin chains.
J Biol Inorg Chem
; 24(2): 247-255, 2019 03.
Article
em En
| MEDLINE
| ID: mdl-30706146
ABSTRACT
Haptoglobin (Hp) binds human hemoglobin (Hb), contributing to prevent extra-erythrocytic Hb-induced damage. Hp forms preferentially complexes with αß dimers, displaying heme-based reactivity. Here, kinetics and thermodynamics of fluoride and azide binding to ferric human Hb (Hb(III)) complexed with the human Hp phenotypes 1-1 and 2-2 (Hp1-1Hb(III) and Hp2-2Hb(III), respectively) are reported (pH 7.0 and 20.0 °C). Fluoride binds to Hp1-1Hb(III) and Hp2-2Hb(III) with a one-step kinetic and equilibrium behavior. In contrast, kinetics of azide binding to and dissociation from Hp1-1Hb(III)(-N3-) and Hp2-2Hb(III)(-N3-) follow a two-step process. However, azide binding to Hp1-1Hb(III) and Hp2-2Hb(III) is characterized by a simple equilibrium, reflecting the compensation of kinetic parameters. The fast and the slow step of azide binding to Hp1-1Hb(III) and Hp2-2Hb(III) should reflect azide binding to the ferric ß and α chains, respectively, as also proposed for the similar behavior observed in Hb(III). Present results highlight the ligand-dependent kinetic inequivalence of Hb subunits in the ferric form, reflecting structural differences between the two subunits in the interaction with some ferric ligands.
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Base de dados:
MEDLINE
Assunto principal:
Azidas
/
Haptoglobinas
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Hemoglobinas
/
Compostos Férricos
/
Fluoretos
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article
País de afiliação:
Itália