RAPID COMMUNICATION
Amino Acids Responsible for Decreased 2, 3-Biphosphosphoglycerate Binding to Fetal Hemoglobin
Kazuhiko Adachi,
Patrick Konitzer,
Jian Pang,
Konda S. Reddy, and
Saul Surrey
From the The Children's Hospital of Philadelphia, Division of Hematology, University of Pennsylvania School of Medicine, Philadelphia, PA; the Department of Biophysics, University of Pennsylvania, Philadelphia, PA; the Departments of Pediatrics and Research, the duPont Hospital for Children, Wilmington, DE; and the Department of Pediatrics, Jefferson Medical College, Philadelphia, PA.
To clarify the role of 
N-terminal Gly, 5 Glu, and 143 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 G1V, S143H, and Hb F G1V, E5P, S143H) 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 G1V, S143H in the absence of 2, 3-BPG was slightly higher than that of normal Hb F. The decrease in oxygen affinities for Hb F G1V, S143H 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 G1V, E5P, S143H in the absence and presence of 2, 3-BPG were much lower than those of Hb F G1V, S143H 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 
5 Pro does not interact directly with 2, 3-BPG in Hb A. Hb F variants such as Hb F G1V, E5P, S143H, which exhibit reduced oxygen affinity, should facilitate design of efficient antisickling fetal Hb variants for potential use in gene therapy for sickle cell disease.
Blood, Vol. 90 No. 8 (July 15), 1997:
pp. 2916-2920
© 1997 by The American Society of Hematology.
