Covalent binding of glutathione to hemoglobin. I. Inhibition of hemoglobin S polymerization.
Thiol reagents react with cysteine beta 93 of hemoglobin and as a result increase the oxygen affinity of hemoglobin. In the present studies we have used a thiol-disulfide exchange between mixed disulfides of hemoglobin and reduced glutathione to attach intracellular glutathione to hemoglobin and to study its antisickling properties. The rates of production of glutathionyl hemoglobin (G-Hb) depend on the structure of the thiol reagent linked to cysteine beta 93. Up to 25% G-Hb can be produced in normal and sickle red cells because of the high intracellular concentration of reduced glutathione. This high level of G-Hb in normal cells increases the oxygen affinity by about 35% and reduces heme-heme interactions. In sickle cells the increased oxygen affinity is associated with an inhibition of sickling of about 70% at 21 mm Hg. Inhibition of polymerization of deoxy HbS is also due to a direct inhibition of intermolecular contacts in the fibers as demonstrated by the increased solubility and the increased delay time of G-HbS compared to deoxy HbS.
D001665:Binding Sites; D003545:Cysteine; D004229:Dithiothreitol / Q000494:pharmacology; D005978:Glutathione / Q000097:blood*; D006451:Hemoglobin, Sickle / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D011485:Protein Binding
D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D046911:Macromolecular Substances; D005978:Glutathione; D003545:Cysteine; D004229:Dithiothreitol