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Solution structure of the P30-trans form of Alpha Hemoglobin Stabilizing Protein (AHSP)
Structural highlights
FunctionAHSP_HUMAN Acts as a chaperone to prevent the harmful aggregation of alpha-hemoglobin during normal erythroid cell development. Specifically protects free alpha-hemoglobin from precipitation. It is predicted to modulate pathological states of alpha-hemoglobin excess such as beta-thalassemia.[1] Publication Abstract from PubMedHemoglobin A (HbA), the oxygen delivery system in humans, comprises two alpha and two beta subunits. Free alpha-hemoglobin (alphaHb) is unstable, and its precipitation contributes to the pathophysiology of beta thalassemia. In erythrocytes, the alpha-hemoglobin stabilizing protein (AHSP) binds alphaHb and inhibits its precipitation. The crystal structure of AHSP bound to Fe(II)-alphaHb reveals that AHSP specifically recognizes the G and H helices of alphaHb through a hydrophobic interface that largely recapitulates the alpha1-beta1 interface of hemoglobin. The AHSP-alphaHb interactions are extensive but suboptimal, explaining why beta-hemoglobin can competitively displace AHSP to form HbA. Remarkably, the Fe(II)-heme group in AHSP bound alphaHb is coordinated by the distal but not the proximal histidine. Importantly, binding to AHSP facilitates the conversion of oxy-alphaHb 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 alphaHb. Molecular mechanism of AHSP-mediated stabilization of alpha-hemoglobin.,Feng L, Gell DA, Zhou S, Gu L, Kong Y, Li J, Hu M, Yan N, Lee C, Rich AM, Armstrong RS, Lay PA, Gow AJ, Weiss MJ, Mackay JP, Shi Y Cell. 2004 Nov 24;119(5):629-40. PMID:15550245[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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