Amino acids responsible for decreased 2,3-biphosphoglycerate binding to fetal hemoglobin.
To clarify the role of gammaN-terminal Gly, gamma5 Glu, and gamma143 Ser in 2,3-biphosphosphoglycerate (BPG) binding to fetal hemoglobin (Hb F), we engineered and produced normal human Hb F and two Hb F variants (Hb F gammaG1V, gammaS143H, and Hb F gammaG1V, gammaE5P, gammaS143H) using a yeast expression system and then compared their oxygen-binding properties with those of native human Hb F and adult Hb (Hb A). Oxygen affinity of Hb F gammaG1V, gammaS143H in the absence of 2,3-BPG was slightly higher than that of normal Hb F. The decrease in oxygen affinities for Hb F gammaG1V, gammaS143H with increasing 2,3-BPG concentrations was larger than that of normal Hb F, but significantly less than that of Hb A. In contrast, oxygen affinities of Hb F gammaG1V, gammaE5P, gammaS143H in the absence and presence of 2,3-BPG were much lower than those of Hb F gammaG1V, gammaS143H and were similar to those of Hb A. These results indicate that differences between Pro and Glu at the A2 position in the A helix in Hb A and Hb F, respectively, are critical for reduced binding of 2,3-BPG to Hb F, even though beta5 Pro does not interact directly with 2,3-BPG in Hb A. Hb F variants such as Hb F gammaG1V, gammaE5P, gammaS143H, which exhibit reduced oxygen affinity, should facilitate design of efficient antisickling fetal Hb variants for potential use in gene therapy for sickle cell disease.
Adachi
K
K
The Children's Hospital of Philadelphia, Division of Hematology, University of Pennsylvania School of Medicine, 19104, USA.
Konitzer
P
P
Pang
J
J
Reddy
K S
KS
Surrey
S
S
D019794:2,3-Diphosphoglycerate / Q000378:metabolism*; D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D002942:Circular Dichroism; D004588:Electrophoresis, Cellulose Acetate; D005312:Fetal Blood / Q000737:chemistry; D005319:Fetal Hemoglobin / Q000378:metabolism*; D006441:Hemoglobin A / Q000378:metabolism; D006801:Humans; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D013054:Spectrophotometry, Atomic
D000596:Amino Acids; D019794:2,3-Diphosphoglycerate; D006441:Hemoglobin A; D005319:Fetal Hemoglobin; D010100:Oxygen