|
|
Blood, 4 June 2009, Vol. 113, No. 23, pp. 5961-5969.
Prepublished online as a Blood First Edition Paper on April 6, 2009; DOI 10.1182/blood-2008-12-196030.
 Previous Article | Table of Contents | Next Article 
RED CELLS, IRON, AND ERYTHROPOIESIS
Analysis of human  globin gene mutations that impair binding to the hemoglobin stabilizing protein
Xiang Yu1,
Todd L. Mollan2,
Andrew Butler3,
Andrew J. Gow3,
John S. Olson2, and
Mitchell J. Weiss4
1 Cell and Molecular Biology Graduate Group, University of Pennsylvania, Philadelphia;
2 Department of Biochemistry and Cell Biology, Rice University, Houston, TX;
3 Department of Pharmacology, Rutgers University, Piscataway, NJ; and
4 Division of Hematology, Children's Hospital of Philadelphia, PA
Alpha hemoglobin stabilizing protein (AHSP) reversibly binds nascent  globin to maintain its native structure and facilitate its incorporation into hemoglobin A. Previous studies indicate that some naturally occurring human globin mutations may destabilize the protein by inhibiting its interactions with AHSP. However, these mutations could also affect hemoglobin A production through AHSP-independent effects, including reduced binding to β globin. We analyzed 6 human globin variants with altered AHSP contact surfaces. Alpha globin amino acid substitutions H103Y, H103R, F117S, and P119S impaired interactions with both AHSP and β globin. These mutations are destabilizing in biochemical assays and are associated with microcytosis and anemia in humans. By contrast, K99E and K99N globins bind β globin normally but exhibit attenuated binding to AHSP. These mutations impair protein folding and expression in vitro and appear to be mildly destabilizing in vivo. In Escherichia coli and erythroid cells, globin K99E stability is rescued on coexpression with AHSP mutants in which binding to the abnormal globin chain is restored. Our results better define the biochemical properties of some globin variants and support the hypothesis that AHSP promotes globin chain stability during human erythropoiesis.
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
|
|
