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Biophysical characterization of the alpha-globin binding protein alpha-hemoglobin stabilizing protein
journal contribution
posted on 2023-05-17, 02:59 authored by David GellDavid Gell, Kong, Y, Eaton, SA, Weiss, MJ, Mackay, JPα-Hemoglobin stabilizing protein (AHSP) is a small (12 kDa) and abundant erythroid-specific protein that binds specifically to free α-(hemo)globin and prevents its precipitation. When present in excess over β-globin, its normal binding partner, α-globin can have severe cytotoxic effects that contribute to important human diseases such as β-thalassemia. Because AHSP might act as a chaperone to prevent the harmful aggregation of α-globin during normal erythroid cell development and in diseases of globin chain imbalance, it is important to characterize the biochemical properties of the AHSP·α-globin complex. Here we provide the first structural information about AHSP and its interaction with α-globin. We find that AHSP is a predominantly α-helical globular protein with a somewhat asymmetric shape. AHSP and α-globin are both monomeric in solution as determined by analytical ultracentrifugation and bind each other to form a complex with 1:1 subunit stoichiometry, as judged by gel filtration and amino acid analysis. We have used isothermal titration calorimetry to show that the interaction is of moderate affinity with an association constant of 1 × 107 M-1 and is thus likely to be biologically significant given the concentration of AHSP (∼0.1 mM) and hemoglobin (∼4 mm) in the late pro-erythroblast.
History
Publication title
Journal of Biological ChemistryVolume
277Issue
43Pagination
40602-40609ISSN
0021-9258Department/School
Menzies Institute for Medical ResearchPublisher
Amer Soc Biochemistry Molecular Biology IncPlace of publication
9650 Rockville Pike, Bethesda, USA, Md, 20814-3996Repository Status
- Restricted