Fluoride and azide binding to ferric human hemoglobin:haptoglobin complexes highlights the ligand-dependent inequivalence of the α and β hemoglobin chains

Abstract Haptoglobin (Hp) binds human hemoglobin (Hb), contributing to prevent extra-erythrocytic Hb-induced damage. Hp forms preferentially complexes with αβ 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 (Hp1-1:Hb(III) and Hp2-2:Hb(III), respectively) are reported (pH 7.0 and 20.0 °C). Fluoride binds to Hp1-1:Hb(III) and Hp2-2:Hb(III) with a one-step kinetic and equilibrium behavior. In contrast, kinetics of azide binding to and dissociation from Hp1-1:Hb(III)(–$ N_{3} $−) and Hp2-2:Hb(III)(–$ N_{3} $−) follow a two-step process. However, azide binding to Hp1-1:Hb(III) and Hp2-2:Hb(III) is characterized by a simple equilibrium, reflecting the compensation of kinetic parameters. The fast and the slow step of azide binding to Hp1-1:Hb(III) and Hp2-2:Hb(III) should reflect azide binding to the ferric β 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. Graphical abstract.

Medienart:

Artikel

Erscheinungsjahr:

2019

Erschienen:

2019

Enthalten in:

Zur Gesamtaufnahme - volume:24

Enthalten in:

Journal of biological inorganic chemistry - 24(2019), 2 vom: 31. Jan., Seite 247-255

Sprache:

Englisch

Beteiligte Personen:

Ascenzi, Paolo [VerfasserIn]
di Masi, Alessandra [VerfasserIn]
De Simone, Giovanna [VerfasserIn]
Gioia, Magda [VerfasserIn]
Coletta, Massimo [VerfasserIn]

Links:

Volltext [lizenzpflichtig]

Themen:

Azide binding
Fluoride binding
Human haptoglobin 1-1:hemoglobin complex
Human haptoglobin 2-2:hemoglobin complex
Kinetics
Thermodynamics

Anmerkungen:

© Society for Biological Inorganic Chemistry (SBIC) 2019

doi:

10.1007/s00775-019-01642-9

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

OLC204945645X