Dynamics of α-Hb chain binding to its chaperone AHSP depends on heme coordination and redox state.
Biochim Biophys Acta
; 1840(1): 277-87, 2014 Jan.
Article
em En
| MEDLINE
| ID: mdl-24060751
ABSTRACT
BACKGROUND:
AHSP is an erythroid molecular chaperone of the α-hemoglobin chains (α-Hb). Upon AHSP binding, native ferric α-Hb undergoes an unprecedented structural rearrangement at the heme site giving rise to a 6th coordination bond with His(E7).METHODS:
Recombinant AHSP, WT α-HbAHSP and α-Hb(HE7Q)AHSP complexes were expressed in Escherichia coli. Thermal denaturation curves were measured by circular dichroism for the isolated α-Hb and bound to AHSP. Kinetics of ligand binding and redox reactions of α-Hb bound to AHSP as well as α-Hb release from the α-HbAHSP complex were measured by time-resolved absorption spectroscopy.RESULTS:
AHSP binding to α-Hb is kinetically controlled to prevail over direct binding with ß-chains and is also thermodynamically controlled by the α-Hb redox state and not the liganded state of the ferrous α-Hb. The dramatic instability of isolated ferric α-Hb is greatly decreased upon AHSP binding. Removing the bis-histidyl hexacoordination in α-HbH58(E7)QAHSP complex reduces the stabilizing effect of AHSP binding. Once the ferric α-Hb is bound to AHSP, the globin can be more easily reduced by several chemical and enzymatic systems compared to α-Hb within the Hb-tetramer.CONCLUSION:
α-Hb reduction could trigger its release from AHSP toward its final Hb ß-chain partner producing functional ferrous Hb-tetramers. This work indicates a preferred kinetic pathway for Hb-synthesis. GENERALSIGNIFICANCE:
The cellular redox balance in Hb-synthesis should be considered as important as the relative proportional synthesis of both Hb-subunits and their heme cofactor. The in vivo role of AHSP is discussed in the context of the molecular disorders observed in thalassemia.Palavras-chave
AHSP; AHSP(WT); AHSP:α-Hb; Alpha-hemoglobin stabilizing protein (AHSP); Chaperone; Cyt b5; Erythropoiesis; GST; Hb; Heme hexacoordination; Hemoglobin; MetHb; Ngb; PBS; RBCs; ROS; alpha hemoglobin-stabilizing protein; complex formed between WT α-Hb chain and recombinant human wild type AHSP; ferric heme; glutathione S-transferase; hemin; human adult hemoglobin; neuroglobin; oxidized Hb; phosphate-buffered saline; reactive oxygen species; recombinant human wild type AHSP with an N-terminal Gly-Pro-Leu-Gly-Ser peptide; recombinant soluble domain of human membrane-bound cytochrome b5; red blood cells
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Hemoglobina A
/
Proteínas Sanguíneas
/
Chaperonas Moleculares
/
Heme
Limite:
Humans
Idioma:
En
Ano de publicação:
2014
Tipo de documento:
Article