Molecular mechanism of AHSP-mediated stabilization of α-hemoglobin

Liang Feng, David A. Gell, Suiping Zhou, Lichuan Gu, Yi Kong, Jianqing Li, Min Hu, Nieng Yan, Christopher Lee, Anne M. Rich, Robert S. Armstrong, Peter A. Lay, Andrew J. Gow, Mitchell J. Weiss, Joel P. MacKay, Yigong Shi

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136 Scopus citations


Hemoglobin A (HbA), the oxygen delivery system in humans, comprises two α and two β subunits. Free α-hemoglobin (αHb) is unstable, and its precipitation contributes to the pathophysiology of β thalassemia. In erythrocytes, the α-hemoglobin stabilizing protein (AHSP) binds αHb and inhibits its precipitation. The crystal structure of AHSP bound to Fe(II)-αHb reveals that AHSP specifically recognizes the G and H helices of αHb through a hydrophobic interface that largely recapitulates the α11 interface of hemoglobin. The AHSP-αHb interactions are extensive but suboptimal, explaining why β-hemoglobin can competitively displace AHSP to form HbA. Remarkably, the Fe(II)-heme group in AHSP bound αHb is coordinated by the distal but not the proximal histidine. Importantly, binding to AHSP facilitates the conversion of oxy-αHb to a deoxygenated, oxidized [Fe(III)], nonreactive form in which all six coordinate positions are occupied. These observations reveal the molecular mechanisms by which AHSP stabilizes free αHb.

Original languageEnglish (US)
Pages (from-to)629-640
Number of pages12
Issue number5
StatePublished - Nov 24 2004

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)


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