Structure of oxidized $\alpha$-haemoglobin bound to AHSP reveals a protective mechanism for haem. Feng, L., Zhou, S., Gu, L., Gell, D. A., Mackay, J. P., Weiss, M. J., Gow, A. J., & Shi, Y. Nature, 435(7042):697–701, jun, 2005.
Structure of oxidized $\alpha$-haemoglobin bound to AHSP reveals a protective mechanism for haem [link]Paper  doi  abstract   bibtex   
The synthesis of haemoglobin A (HbA) is exquisitely coordinated during erythrocyte development to prevent damaging effects from individual $\alpha$- and $\beta$-subunits. The $\alpha$-haemoglobin-stabilizing protein (AHSP) binds $\alpha$-haemoglobin ($\alpha$Hb), inhibits the ability of $\alpha$Hb to generate reactive oxygen species and prevents its precipitation on exposure to oxidant stress. The structure of AHSP bound to ferrous $\alpha$Hb is thought to represent a transitional complex through which $\alpha$Hb is converted to a non-reactive, hexacoordinate ferric form. Here we report the crystal structure of this ferric $\alpha$Hb-AHSP complex at 2.4 A resolution. Our findings reveal a striking bis-histidyl configuration in which both the proximal and the distal histidines coordinate the haem iron atom. To attain this unusual conformation, segments of $\alpha$Hb undergo drastic structural rearrangements, including the repositioning of several $\alpha$-helices. Moreover, conversion to the ferric bishistidine configuration strongly and specifically inhibits redox chemistry catalysis and haem loss from $\alpha$Hb. The observed structural changes, which impair the chemical reactivity of haem iron, explain how AHSP stabilizes $\alpha$Hb and prevents its damaging effects in cells.
@article{Feng2005,
abstract = {The synthesis of haemoglobin A (HbA) is exquisitely coordinated during erythrocyte development to prevent damaging effects from individual $\alpha$- and $\beta$-subunits. The $\alpha$-haemoglobin-stabilizing protein (AHSP) binds $\alpha$-haemoglobin ($\alpha$Hb), inhibits the ability of $\alpha$Hb to generate reactive oxygen species and prevents its precipitation on exposure to oxidant stress. The structure of AHSP bound to ferrous $\alpha$Hb is thought to represent a transitional complex through which $\alpha$Hb is converted to a non-reactive, hexacoordinate ferric form. Here we report the crystal structure of this ferric $\alpha$Hb-AHSP complex at 2.4 A resolution. Our findings reveal a striking bis-histidyl configuration in which both the proximal and the distal histidines coordinate the haem iron atom. To attain this unusual conformation, segments of $\alpha$Hb undergo drastic structural rearrangements, including the repositioning of several $\alpha$-helices. Moreover, conversion to the ferric bishistidine configuration strongly and specifically inhibits redox chemistry catalysis and haem loss from $\alpha$Hb. The observed structural changes, which impair the chemical reactivity of haem iron, explain how AHSP stabilizes $\alpha$Hb and prevents its damaging effects in cells.},
annote = {cited By 85},
author = {Feng, Liang and Zhou, Suiping and Gu, Lichuan and Gell, David A. and Mackay, Joel P. and Weiss, Mitchell J. and Gow, Andrew J. and Shi, Yigong},
doi = {10.1038/nature03609},
issn = {0028-0836},
journal = {Nature},
month = {jun},
number = {7042},
pages = {697--701},
pmid = {15931225},
title = {{Structure of oxidized $\alpha$-haemoglobin bound to AHSP reveals a protective mechanism for haem}},
url = {http://www.nature.com/articles/nature03609},
volume = {435},
year = {2005}
}

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